Kingdom Rush

Kingdom Rush (developed by Ironhide Studios) is a Tower Defense game set in a fantasy world, where you play as the general trying to stop the evil lich Vez'naz from taking over the world. It involves placing towers in allocated paths along set paths. There are four towers-Barracks, Artillery, Archers, Mages, each with their own disadvantages and advantages. Each tower has 3 upgrade levels, improvements in the tech tree, and two branching 4th upgrade levels--you choose one or the other. Better explained:

Archers typically form the backbone of the player's damage dealing forces, with a high fire rate and good damage, as well as upgrades in the tech tree allowing them to pierce armor. They are also capable of attacking flying foes at any upgrade level. Generally, the tower with the highest numbers on the field (though not necessarily a majority) is the archer tower. Their Level 4 options are the Ranger Hideout (which focuses on Damage Over Time, controlling foes with vines, etc. and high fire rates but low damage with individual shots) and the Musketeer Garrison (which focuses on precision shots which is hard hitting but have lower rate of fire, as well as some AOE abilities).

The primary role of the Barracks is to slow foes down by engaging them so the other towers can unleash their punishment on them. As such, their upgrades tend to focus on increasing health and damage resistance, eventually doing damage to foes as they get damaged themselves. Barracks are especially good when combined with Reinforcements (see below) to stop the maximum amount of foes. They are incapable of attacking flying units without upgrades. Their Level 4 options are the Holy Order (which summons paladins with high armor and damage resistance that can heal and deal extra damage with holy strikes) and the Barbarian Mead Hall (which summons barbarians that can deal loads of damage to enemies, attack flyers and respawn quite quickly at the cost of some of their resilience).

Mages generally have the strongest individual attacks, and their primary role is to take out armored enemies. Their rates of fire are generally very slow, and they are thus best used when combined with Barracks troops to slow foes down. At higher upgrade levels, they can kill many foes in one hit, though many enemies later on have special magic resistance to counterbalance this. Their Level 4 options are the Arcane Wizard (which can teleport foes backwards on the map and have a Death Ray that instantly kills any foe hit with it) and the Sorcerer Mage (which focuses on Standard Status Effects and summons elementals to help with the melee fighting, as well as being able to cast a Baleful Polymorph.)

Artillery is the main Area of Effect tower. It deals very large amounts of damage to very large amounts of enemies and Splash Damage at the cost of fire rate, which is the slowest in the game. They are most effective when combined with Barracks which cluster the foes and allow the maximum number of enemies to be hit as possible. Their Level 4 options are the Big Bertha (hulking towers with a very powerful but very slow-to-reload bomb and who's abilities include a cluster bomb to strike many opponents and a heat-seaking missile that never misses) and the Tesla X104 (which can strike flying units but is weaker than the Big Bertha, and who's abilities include an overcharge that strikes all nearby enemies and a chain lightning attack that can also strike multiple enemies).

In addition, there are two "special abilities" that can be called upon: the Rain of Fire (which rains meteors down from the sky) and Reinforcements (which summons two villagers as militia to fight off intruders).

Tropes used in Kingdom Rush include:

Airborne Mook: The Gargoyles, Demonic Imps and Rocket Riders.
Anti-Air: At the start of the game, only Mages and Archers can tackle flying enemies, as Artillery and Barracks are defenceless against them. However, the Barracks upgrade to Barbarians allows them to both attack and hinder flying foes, whilst the Artillery gains the tesla X104, which can attack flying foes, and the Big Bertha, which has a heat seeking missile ability to target the flying foes.
Area of Effect: The Artillery make a living off this. Musketeers also have an upgrade that allows them to fire a cluster of shots at an enemy and all its surrounding buddies. The Player-controlled Rain of Fire spell also has this.
Awesome but Practical: Every advanced tower has one of these.
Boom! Headshot!: When the Musketeer's Sniper Shot is successful, the Written Sound Effect is "Headshot!"
Boring but Practical: Reinforcements, especially when fully upgraded, can really save your ass if used correctly.
Black Knight: Highly armored foes, ironically introduced exactly when the Paladins are.
Chain Lightning: The Tesa X104 has an upgrade that does this.
Clown Car Base: All of those soldiers were in that one barracks?
Combat Medic: Shamans.
- Also Paladins from the Holy Order Barracks upgrade, which have a healing spell.
Contractual Boss Immunity: Several bosses are immune to upgrades such as Wrath of the Forrest, Teleportation, Polymorph and Poison Arrows. They could be immune to all non-damaging abilities.
Cool Gate: The teleportation panels in Vez'naz's Dark Tower which allow enemies to bypass some of your defences.
Critical Hit: Archers have a universal upgrade that leads to a chance for this.
Death Ray: The Arcane Wizards have this.
Dem Bones: One of the possible enemies.
Dungeon Bypass: Some enemies have this ability, sometimes, there are also tunnels the enemies can use to bypass your defenses and allowing them to appear further in. High level mages also can be upgraded with the ability to do the reverse.
Enemy Summoner: The Necromancers, whilst supposedly raising the dead, are able to summon skeletons from any place, even where there should logically be no dead, so they are little more than this. The Juggernaut fires Golem Heads to distract your towers from him. Spider Matriarchs can lay eggs that spawn three Spiderlings, who are lightning fast and are a considerable threat.
Evil Overlord: Vez'naz, the main villain.
Excuse Plot: "The kingdom is under attack" is basically the extent of story we get for this, though the individual campaigns at last have believable backgrounds.
Fragile Speedster: Spiderlings!
Heavily Armored Mook: Orcs and later Black Knights.
Hired Guns: The Sylvan elves.
Instant Militia: One of the abilities you get.
Instant Runes: The Arcane Wizards have these for their Teleportation and Death Ray spells.
Klaatu Barada Nikto: One of the phrases uttered by the Arcane Wizards.
Level Grinding: Often the case when you need a particular upgrade; you can go back and get extra stars from Iron and Heroic Challenge Modes.
Lightning Gun: One of the possible final upgrade for the artillery.
Meat Shield: The role of the Barracks troops in general, but this especially applies to the Holy Order's paladins, who have the highest armor available for the player's side and have access to even more damage resilience upgrades as well as healing spells to stay alive.
One-Hit Kill: The Arcane Wizard's Death Ray.
One-Winged Angel: Vez'naz will revive as a demon after you kill him for the first time.
Our Elves Are Different: Mercenaries who fight with Bow and Sword in Accord.
Our Goblins Are Wickeder: And I quote-"Small evil humanoids with no outstanding abilities".
Our Orcs Are Different: "Tough savages with light armor".
Shout-Out: Vez'naz references The Dark Knight and Portal. The Arcane Wizards will shout "Avadakadavra!" when they use their death spell. Some of the barbarians' random names are Erik, Olaf, and Baelog.
Splash Damage: The Artillery attack allows for this, and so it's primary advantage over other towers is its ability to wipe out Zerg Rushes
Supervillain Lair: Vez'naz's awesome Dark Tower serves as the game's final level.
We Have Reserves: You get an archievement for sending a certain amount of soldiers to their deaths.
You Shall Not Pass: Your purpose in the game.
Zerg Rush: Sort of the entire idea behind the game, and Tower Defense games in general, is stopping Zerg Rushes.