Armor-Piercing Attack

"I shoot the hippopotamus with bullets made of platinum,

Because if I use leaden ones, his hide is sure to flatten 'em."

- Hilaire Belloc

So you've been managing well with your current skills, dispatching enemies with your familiar attacks and weapons. Now you've encountered a Heavily Armored Mook. Using your basic attacks and abilities you ... fail to hurt the Mook at all. Not good.

So what do you need? You need Armor Piercing! Basically, it's an attack, weapon, or munition that rips through the armor that your enemies wear (or their special shield, or whatever's protecting them), often as if they had no armor to begin with. Sometimes this goes to the point of Tactical Rock-Paper-Scissors, with the anti-armor weapon useless against foes with no armor; another option is that the weapon or attack will destroy the armor, after which your normal attacks will work. Destroying some kind of armored shell is a pretty common first step in a multi-stage Boss Battle.

This can also be turned against the player; for example, if normally their life bar only decreases once their armor bar is depleted, late-game enemies might get attacks that damage both bars at once, or even ignore the armor bar entirely.

Obviously, this isn't how things work in real life; firstly, even a non-piercing hit to armor can deal damage. This is especially true of soft body armor, but can even affect tanks (a phenomenon called spalling, which some types of anti-tank round attempt to cause). Second, there's no magic on / off state to armor; the only things you can do are to hit it harder, which has limits depending on who's supposed to be using the weapon in question, or hit a smaller area. The latter is how most modern anti-tank weapons work, using either focused jets of molten material (HEAT rounds) or dart-shaped heavy penetrators with sharp tips.

See also Depleted Phlebotinum Shells and Clothing Damage (if the armor is destroyed). Might cross over with Elemental Rock-Paper-Scissors if the armor is made from one element and the skill or weapon uses the opposed element. Not related to Armor-Piercing Slap. May be used in combination with Armor Is Useless and/or One-Hit Polykill.

Tabletop Games

 * Champions
 * The Armor Piercing power advantage reduced defending armor by half versus the attack.
 * The Penetrating power advantage: even if the attack is completely stopped by enemy defenses, a little (averages to 1/6) will always get through.
 * Most modern day RPG's have some kind of armor piercing bullets.
 * Shadowrun had APDS (Armor Piercing Discarding Sabot) bullets for firearms.
 * GURPS has various "armor divisors" from 2 through infinity. For example: in the Ultra-Tech book even handgun bullets can be loaded with the High Explosive Multi-Purpose (HEMP) warhead which reduces the effectiveness of armor to one fifth normal by using a sort of shaped charge.
 * Most weapons in Warhammer 40000 have an armor piercing stat that specifies how good an armor they can bypass (in game terms, it deprives the target of its armor-based saving throw). Power weapons do not allow armour saves to happen against them, ever.
 * Given that most infantry weapons have an AP stat of at least 5, this renders any models with an armour save of 5 or 6 pretty much unprotected against enemy fire. Like the Imperial Guard, who are unfortunate enough to be squishy humans. And armed with a laser gun with no armour piercing value whatsoever.
 * Its fantasy counterpart has Armor Piercing Attack as a special ability of certain weapons, like guns and crossbows. It lowers the target's armor even further (in addition to the modifier based on the strength of the weapon used).
 * The Hero Clix version of the feat card allows any character who wields it to still do 1 damage even if it would normally be reduced to 0. They still have to have at least a damage value of 1, though.
 * A clip of ammunition with this in Mekton Zeta costs four times as much as a normal round and halves the target's armour value. (For a similar price, you can skip attacking the target's mech at all and shoot electric bullets, which bypass armour and directly affect the enemy pilot.)
 * BattleTech offers armor-piercing shells for its standard and light autocannons, which may inflict critical hits -- though no internal structure damage as such -- even through armor. (This is in addition to the usual chance of a lucky roll on the hit location table.) Many players don't consider that effect worth putting up with their reduced accuracy and halved number of shots per ton, though.
 * Earthdawn had armor-defeating hits: basically, if you rolled well enough on your attack role, you could ignore the effect of your target's armor. In addition, some weapons and spells (razor orb being the most notable) were designed to cut through armor so a lower roll could still be an armor defeating hit.
 * In Magic: The Gathering, spells ending in -dict (such as Diabolic Edict), and the annihilator ability, require your opponent sacrifice a card, getting around protection, absorb, indestructability, damage prevention, high toughness, regeneration, and everything else. Unfortunately, your opponent still gets to choose which card he sacrifices.
 * In Dungeons and Dragons 3ed/3.5, a number of attacks can ignore certain categories of defenses, and become a very major part of the strategy in advanced play. Many spells ignore armor; a handfull also ignore spell resistance and saves or deal damage of a type that is virtually impossible to resist - spells with all four of these traits are highly valued. A rogue or ninja's backstab attacks, conversely, ignore dodging and a number of related defenses which are often the best options against magic damage. Lances do not actually negate any defenses outright, but due to the way accuracy and damage reduction function in the game possess characteristics that make them extremely effective against almost all forms of defense.
 * Certain monk builds based on grappling also negate armor.
 * In 3.0, a combination of very high critical hit rates and the buff Bless Weapon were able to negate armor on 60% or more of all attacks. Nerfed in 3.5, where critical buffs cannot stack and are exclusive with any buff that would actually make them worthwhile anyway.

Video Games

 * Ancient Domains of Mystery: There is a weapon called phase dagger that completely ignores the armour of the target. The downside is that on each hit, the game throws at you a message about you easily cutting through the armour, which requires you to press [more] much more often. And the dagger itself doesn't do much damage anyway, making it useful only against Heavily Armored Mooks.
 * Final Fantasy X does this with armored enemies, who require a specific weapon type to get past it. Fortunately, they begin to show up just as you get the biggest Badass around, whose weapons all come with the armor-piercing ability, into your party.
 * In all the Final Fantasy games, Flare and Ultima tend to be armor-piercing attacks.
 * Final Fantasy XII had guns and measures, both of which only calculated the weapon's strength for damage. So while they were good against enemies that had high defenses, it didn't matter how strong a character was when using them. However, it doesn't help that some of the tougher enemies only take a 16th of the damage from the two weapons.
 * In Legend of Dragoon, the group knew they'd stand no chance against the Divine Dragon on normal terms, so they went on a quest to find the Dragon-Block Staff (made specifically for fighting dragons), thus allowing them to fight a significantly de-powered Divine Dragon with a chance of victory (which is funny, because it still manages to be That One Boss).
 * Mass Effect 2 has three different kinds of non-health defenses. Powers and weapons receive damage multipliers against specific defenses. Powers will not perform their full effect against armoured targets (Attempting to knock down a target with a concussive shot while they are protected will just stagger them), but may still damage their protective barrier (and may even be unable to damage targets who are unprotected - Overload, for example, is a counter to shields and synthetic enemies, and does no health damage to organic enemies, only being able to damage their shields)
 * In Aliens Versus Predator 2, Praetorian Xenomorphs are immune to most standard gunfire, and only vulnerable to heavy weapons or special armor-piercing bullets from the lighter ones.
 * Of course, Predator players have to take down Praetorians the manly way: with their armor-piercing spears.
 * One of the Samurai's abilities in Disgaea 3 Absence of Justice allows half of his basic attack's damage to ignore the enemy's defense. There's also a gun skill called Armor Piercing, but it subverts it by not ignoring the opponent's defense in any way.
 * FEAR 2 has several weapons which disregard or degrade the functionality of armor, both for enemies and the player.
 * To be more specific: all weapons, especially in the first game, deal part of the damage directly to the health. However, in most weapons the damage that isn't absorbed by the armor is a very small fraction of the total. However, there's a weapon in each game (the Penetrator in the first game, the Hammerheadin the second) that ignores armor almost completely, making them true examples of this trope.
 * The Wing Commander series, starting with Wing Commander 2, features capital ships with shields or armor that is too heavy to be threatened by the weapons normally carried by fighters and smaller warships. To overcome this, heavy fighters and bombers can carry large, bulky torpedoes which are designed to "phase" through the enemy's shields and strike with a nuclear or antimatter warhead. The process of finding the right frequency for the shields justifies you needing to make long approaches towards an enemy ship which is actively trying to kill you before you can finally release the torpedo (and hope it doesn't get shot down itself). Later in the series, it goes back and forth between whether non-torpedo fighter weapons can or can't harm capital warships.
 * Warcraft 3 has various damage and armor types. Certain damage types may deal more or less damage depending on armor type, while armour amount also influences how much damage is received through percentage reduction. One type of armor (Divine) is practically immune to any damage except one type of damage (Chaos). Spells tend to ignore physical armor when inflicting damage, but may instead be affected by some abilities or fail to work altogether on some unit classifications.
 * In World of Warcraft, this trope used to exist as Armor Penetration, a very desirable stat for classes that mainly inflict physical damage, such as rogues and warriors, but it was removed due to balance issues, though those two retain abilities to reduce the opponent's armor with a debuff for the benefit of their allies.
 * Speaking of Blizzard games, both Starcraft and Starcraft II also have two different armor/damage systems in play. In both games, the amount of armor on a unit subtracts from the damage dealt by an attacking unit: if an attacker deals 3 damage and the target has 2 armor, 2 damage will be subtracted from the attack and only 1 damage will actually be dealt. In gameplay terms, this means that weaker attacks will be disproportionately less effective than higher damage attacks against armor, although this could be easily overcome by Spam Attack from faster attacks or through sheer numbers.
 * As for the secondary armor/damage systems, Starcraft has one in which different attack types may do half, three-quarters, or full damage depending on unit type, with "concussion" type attacks dealing full damage to "light" units, three-quarters damage to "medium" units and half damage to "heavy" units. Starcraft II does away with the system, opting instead for one in which some units receive a bonus to attack against certain unit types. A Terran Marauder for example, deals 10 damage to most targets, but receives an extra 10 damage against any "Armored" type ground unit for a total of 20 damage. Like Warcraft III, abilities in both games ignore physical armor but may be affected by unit type, with Irradiate capable of dealing up to 200 damage on biological units but remaining completely ineffective against mechanical ones.
 * In Fallout 3 the Deathclaw Gauntlet ignores armor entirely.
 * Largely averted in Fallout 2 but only due to bad design. Hollow-point and other "regular" ammo is generally superior to armor-piercing ammo in any given situation with the AP Needler ammo and the AP rocket (!) ammo being exceptions.
 * The latest release of the Fallout 2 Restoration Project includes an option to fix AP ammo modifiers, making them work as intended.
 * Played straight in Fallout: New Vegas - normal ammo is jack-of-all, master-of-none, hollowpoints work great against soft targets, AP does better against enemies with good armor. With a special perk, you can unlock a wide variety of specialized hand-load munitions: .308 and 5mm gets the Jacketed Soft Point (basically an uprate of the basic Ball ammo), the revolver/lever rifle calibers get Semi-Wadcutter or Jacketed Flat Point rounds (moderate damage boost + modest armor-piercing power), 5.56mm and .50cal get Match grade (modest damage boost, big accuracy bonus), and pistol/SMG calibers get Jacketed Hollow Point (basically more balanced hollow points). Explosive weapons can load a variety of different munitions as well. Energy weapons are a bit different; they have varying power cell charge grades you can load them with, each grade doing more damage at the cost of greater wear on the already frail energy weapons. After complaints about inherent weakness of energy weapons, one of the many resultant buffs to that weapon category included inherent armor piercing power in all cell power grades, even the basic.
 * A couple of rarer Fallout: New Vegas melee weapons have 'ignores DT/DR' listed in their description. This amounts to dealing all their damage straight to an enemy's HP. One notable example of such a weapon is the aptly named Ripper, a chainsaw short sword. There is also a perk that allows any of the player's melee attacks to ignore up to 15 points of damage threshold.
 * Featured in Paper Mario with Watt, whose basic attack ignores the enemy's defense (making her one of the most useful partners in the game, especially against high-defense enemies), as well as badges which would apply this property to your Jump or Hammer attacks. (Items and the Star Storm power also ignore defense.) The Thousand-Year Door also features said badges (and items/damage-dealing Star Powers), and included Yoshi, whose spit attack had this property (and was needed to beat a mid-level boss who pretty much had infinite defense), as well as the secret character, whose attack is literally an Armor-Piercing Slap.
 * In Master of Magic for units with Armor Piercing attack a target has effectively 1/2 (rounded down) of its normal defense value.
 * In Master of Orion 2 some weapons can be made in armor-piercing variants (and some in shield-piercing, for that matter) so that damage that passes through armor/shields is applied to the target ship's internals immediately.
 * Heavy and Xentronium armor negate armor bypassing, but neither can protect against an attacker equipped with an Achilles Targeting Unit device. Shield piercing weapons can be stopped with the Hard Shields device.
 * In Impossible Creatures, creatures that attack with quills or horns will bypass a portion of the enemy's defense.
 * Iji features this due to the fact that everything is made of Nanotechnology. To wit, small arms fire such as the machine gun or pulse rounds will chip away at your armour (which is really more of a forcefield) until it is depleted at which point a Hit Point is sacrificed to replenish it. However anything which hits you (as in, a rocket, BFG round or a punch) will deal actual damage to your body directly (and send you flying across the room to boot).
 * Starting in Space Empires IV, weapons can now skip armor, in addition to shields.
 * The armor piercing tech in Sword of the Stars. It makes kinetic weapons more accurate and less likely to bounce off the hull, though you get less actual damage in return. The Polarized Plasmatics sub-family will deal extra damage depending on the extra health granted by armour upgrades. Gluonic Torpedoes go through Deflectors and Disruptors, while Mesonic Torpedoes go through all shields other than Meson Shields. Shield Breaker Rounds can bring down all shields, though they don't do any actual damage to the ship.
 * The Terran EMP Shockwave in Starcraft destroys the shields of anything it hits. Not very useful against the Terran or Zerg who don't have shields at all, but a Protoss Archon has 350 shields and 10 health...
 * Borderlands: one of Mordecai's skills enables him to bypass enemy shields. Against the Guardians, their health bars being tiny, it is absolutely devastating.
 * UFO Aftermath has no less that seven damage types: soft, universal, hard, laser, plasma, burn (fire and acid), paralyze and warp (the more armor you have, the more it hurts). Transgenants and armors have separate resistances for each. There is an eighth type referred to as "exception" for a few weapons like the psionic crusher.
 * Company of Heroes gives AP bullets and shells as special abilities for American and British machine guns and AT guns. The former ability turns the dedicated anti-infantry HMG into a feared light-vehicle counter, while the latter boosts the penetration of the AT guns. As the British 17pdr is already one of the best antiarmor weapons in the game, the AP-Discarding Sabot ability makes it one of the few weapons that can counter King Tigers.
 * While traditionally in Armored Core series, Attack Power is the only attribute to watch out for weapons (meaning, how much you need to pump it to any given target to make them go kablooey), 4/for Answer introduced the Force Field-like Primal Armor and consequently, "PA Penetration". Energy weapons, sniper rifles and railguns do this job really well, and since about a good 4/5ths of the game's armor isn't exactly energy-weapon proof, this can only go wrong, were it not for the balancer mechanics.
 * Ragnarok Online not only has weapons that ignore defense, but a dagger called the Ice Pick, which isn't reduced by the target's defense and then proceeds to do more damage depending on how much defense it had. Wearing armor actually makes you take more damage. Thankfully, they are quite rare.
 * In Guild Wars, a few skills have an "armor penetrating ability" reducing a target's armor by a percent against the one attack. Due to how armor works (Extra armor is multiplicative in how much damage it reduces), this has a varying effect depending on the amount of armor. Guild Wars weapon skills that add damage also add a fixed amount of damage, that is unaffected by armor, making them useful against highly armored targets.
 * Pokémon has Brick Break, which breaks any Reflect and Light Screen shields the opponent has set up before damaging the opponent, as well as moves like Chip Away and Secret Sword, which do damage while disregarding opponent's stat boosts in defenses.
 * The Abilities Unaware and Infiltrator ignore stat changes and Reflect/Light Screen respectively.
 * In the Total War series certain units (such as longbowmen or those armed with axes in Medieval I and II) actually put heavily armored units, including those with the extremely expensive armory upgrades, at a disadvantage with this ability.
 * Post-Marian Reforms legionaries in Rome: Total War can shrug off almost any kind of missile attack due to their heavy armour, but a volley of armour-piercing javelins from the right angle can devastate them. Especially fun with Bull Warriors, who have very poor defence for their price but sport the most pimped-out AP missile attack stats of any unit in the game.
 * In Soldier of Fortune, high-power weapons such as the sniper rifle can pierce both the player's and enemy's armor.
 * The Pierce skill in Shin Megami Tensei Nocturne, which allows those who have it to ignore the enemies' elemental resistances, immunities, and drains (but not repels). You get it just in time, too, since that's the point in the game when your randomly encountered enemies may have as many as four or five out of eleven elements be useless against them. Having the skill, and jumping through a few hoops to be able to get it on your Mons, changes the last part of the game from insanely hard to merely sanely hard.
 * Perfect Dark has the Callisto NTG's Secondary Fire setting (High-Impact Shells) and the Farsight sniper rifle. Both will make short work of any shield.
 * Turned against the player in Killing Floor - the Siren's scream ignores armor entirely, while attacks from the Fleshpound and Patriarch typically damage both health and armor.
 * Deus Ex Human Revolution has a realistic take on this: AP mods for your weapons are most useful if the enemy has heavy armour, but don't do much better than normal rounds against lightly-armoured enemies.
 * But then there is the upgrade for the pistol, which makes every shot from it ignore armor. Granted, the pistol isn't very powerful, but one or two headshots will still take out every single mook, heavily-armored or not.
 * Star Ruler has weapons that partially and completely ignore armour, but usually don't do that much actual damage. The Galactic Armory mod adds weapons that are good at killing shields but don't do anything to armor or health.
 * X-COM: UFO Defense and Terror from the Deep starts you with armor piercing weapons. Subverted, since that's only the damage type rather than the ability, and the non-armor piercing attacks are better at breaking through armor. To be more specific, the armor piercing weapons won't overcome the high armor and damage reduction of Lobstermen and Triscenes.
 * In Mega Man Battle Network there are four kinds of armor that can be pierced - Shielding (which yields to Break), Shadow (which yields to Sword), Barriers and Auras (which yield to Wind), and Invisible (which yields to Cursor).
 * Mega Man Star Force retains most of these except for the Cursor-Invisible relationship. You can still bypass Mercy Invincibility under certain circumstances, though.
 * Bioshock's pistol and machine gun both have variant armor piercing rounds, as well as standard slugs and anti-personnel rounds. Everything was more vulnerable to one and less vulnerable to the other, with the armor piercing being useful against machinery and Big Daddies, while anti-personnel pistol rounds would one-shot most splicers.
 * Battlefield 2 had an unlockable anti-materiel sniper rifle for the sniper class, the M95. It's main claim to infamy among the player base was its ability to snipe the pilots of helicopters through their armored canopy glass, something no other gun would do.
 * Command and Conquer Generals and Zero:Hour subvert it by giving the GLA upgrades for armor-piercing bullets and rockets, but those merely increase damage dealt by units using them by 25%.
 * The Mass Driver in the X-Universe games. The weapon will ignore ship shields (which is 90% of a ship's overall health, generally) and damage the ship's hull directly. Mounted en-mass, this small, fighter based weapon is hilariously effective at killing 4 kilometer long destroyers.
 * In King Arthur: The Roleplaying Wargame, certain units can get the armour piercing trait, which reduces enemy armour by 50%. Oddly enough no archer units can get it, but then again King Arthur's archer units are generally considered Game Breakers already and probably don't need any more help.
 * Arcanum has two guns, both BFGs, that do a sort of this. Blade Launcher ignores Armor Class, allowing you to hit more often (and is the second most powerful gun), while Riffled Cannon ignores Damage Resistance, allowing you to do full damage each time you hit. They both, however, consume 6 bullets per shot.
 * This type of attack is nearly mandatory in World of Tanks - not every gun has good HE damage, meaning that often times your ability to deal damage relies entirely on penetrating the enemy's armor from any direction possible.