Finger Firearms

Various parts of the body have been weaponized in fiction and the fingers are no exception despite their small size. Aside from Rule of Cool, the two most common reasons given for this setup are increased firepower and concealment.

Firepower

Fingers weaponized for firepower are usually a specific variation of the Arm Cannon which involves placing a ranged weapon in every finger and occasionally the thumb as well. Smaller machines may have all fingers linked to a common magazine or ammo management system while larger units can have a separate system in the same finger as its gun. There are also cases where the fingers are merely barrels.

This layout is more often used in 'raw power' machines to indicate their destructive ability. The implication is that the unit has many times the firepower of a grunt's main weapon- by having eight or ten of that weapon in its hands alone.

The primary claimed benefit of this design is that it offers More Dakka without sacrificing finger articulation. This ignores the fact that flexible or folding barrels would severely reduce the durability of the guns. Proposed workarounds include housing the entire weapon system in the fingertips, reducing the power of the weapons, making all the fingers rigid rather than articulated or having articulated fingers that go rigid before firing- all of which sacrifice either hand or weapon functionality. In the end, Rule of Cool is the only proper justification.

Pay special attention to the fingers of a Humongous Mecha if they appear to be flexible hollow tubes or if they sport openings or lenses at the ends because these indicate guns. 'Mittens' with rows of barrels are sometimes used by designers who want to mix things up, though these are even less practical as they lose all but the most basic hand functions. Some less humanoid designs may have hand-mounted guns that double as fingers rather than fingers with guns inside, usually in cases where the machine has less than five fingers on each hand.

Concealment

Concealed finger guns can be made virtually indistinguishable from unarmed fingers, particularly if the user's unarmed fingers also look mechanical. Any gun parts that appear on security scans can be handwaved as part of the hand's mechanisms (which they are). Mechanical or mechanically augmented characters who have not previously been shown with weapons can be revealed to sport these without stretching Willing Suspension of Disbelief.

Apart from the design difficulties listed in the firepower section, concealed finger guns also need an even greater degree of miniaturization or integration with the rest of the hand to keep them from being detected, placing further limits on their functionality. Cruder designs that impede the function of the fingers to allow greater power also make detection easier. Finally, risk of detection by internal scans complicates the inclusion of any built-in magazine as most ammunition has a distinctive appearance, limiting the guns to a small number of shots per weapon if solid rounds are needed.

Due to all these limitations, concealed finger guns are usually used for assassination or self defense. However, Humongous Mecha may make effective use of this design by concealing anti-personnel weapons in their fingers- these may not be effective on other large machines but are enough for infantry and light vehicles or aircraft.

NOTE: Guns installed in the metacarpal region (i.e. behind the base of the finger or even further back) should go under Arm Cannon, Power Palms or Hand Blast instead. For the gesture involving making a gun with one's fingers, see Finger Gun. The use of said gesture to channel magic or psionics belongs there as well.

Examples of Finger Firearms include:

Firepower

Anime and Manga

Since the Zeong, Gundam series have occasionally put beam guns in the fingers of enemies they want to make especially threatening. The earlier Gouf from the same series had machine gun fingers.
Giant Robo has missile launchers in its fingers.
Gunbuster fires its Buster Missiles from its fingertips.
- Several machines from the sequel Diebuster have finger guns as well.
004 from Cyborg 009 has finger machine guns as part of his arsenal.
The Moskas in Katekyo Hitman Reborn fire out of their fingers and Mini Moska fires popcorn out of his fingers.
Among many other armaments, the cyborg Grey the Ninelives had these in the anime of Trigun.
One of Blackbeard's henchmen in One Piece has these.
Voltes V's Finger Missiles.

Comics

A somewhat obscure Marvel Comics villain named Professor Power (Who isn't related to Marvel's other "Professor Power") fought many heroes using Power Armor. One version of the armor included guns located in each fingertip of his gauntlets which he used in a fight against Spider-Man and the original members of the X-Men.

Live Action Television

Mighty Morphin Power Rangers had the Dragonzord launch missiles from its fingertips.
- The Delta Command Megazord of Power Rangers SPD did the same with lasers.
- In Power Rangers Jungle Fury, the Rhino Ranger's arm-mounted weapon had laser barrels on one side, looking similar to fingers when that side was used.
The 1974 incarnation of Mechagodzilla could fire missiles from his fingertips.

Tabletop RPG

Shadowrun. Guns in cybernetic fingers were first mentioned in the 2nd Edition Cybertechnology supplement.
Warhammer 40,000
- Obliterators are infected with a "virus" that turns their whole body into Shapeshifter Weapon. They sometimes manifest this trope (especially older models).
- Baleful Eye -- a rare type of bionic eye with high-powered laser gun.
- Older versions of 40K had the Jokaero relics known as digital weapons: miniaturized versions of lasguns, flamers and needleguns that could fitted onto fingers like rings. They also popped up in the Spin-Offs -- Warhammer 40,000 Roleplay series and (as equipment cards) boardgame Space Crusade.

Videogames

In Xenogears, Maria's Seibzehn has missile launchers in its fingers.
The WA-FINGER weapon and its variants in the Armored Core series are multi-barreled machine guns designed to look like hands, probably just to justify the name.
Aigis from Persona 3 has machine gun fingers fed by an external drum magazine.
In Super Mario RPG, one of Geno's weapons is the Finger Shot, which fires bullets out of each of his fingers.
The SRX from the Super Robot Wars series, due to its fingers being formed from the shoulder cannons of one of its components.

Concealment

Film

The assassin Mr. Igoe in Innerspace has a mechanical hand, which in one scene actually fires a bullet from the tip of its index finger - thereby forever one-upping the small child who had pointed his own finger gun at him. (Kid was fine. His balloon wasn't.)
X 2 X Men United: featured a version of Deathstryke who could extend adamantium spines from her fingers.

Literature

Foaly armed Commander Root with the concealed variety in Artemis Fowl because he couldn't go into a hostage negotiation obviously armed.
Honor Harrington has a gun built into her finger and, from the description, her hand does move into something approximating the traditional finger gun position when she fires it.
In Timothy Zahn's The Cobra Trilogy, the Cobra guerrilla cyborgs had a laser built into each little finger.

Live Action Television

From Get Smart: "Would you believe this finger is a real gun?"
- They do find it hard to believe, so Max fires the gun in the air to prove otherwise. Unfortunately it's single shot. Max later reveals that it has a second shot ... and promptly fires it into the air.
- On one show Max is kidnapped and subjected to a Manchurian Agent treatment - they have to let him 'escape' to avoid suspicion, but he repeatedly misses opportunities handed to him. At one point an agent approaches him, he raises a finger and the agent 'surrenders', wise to the old 'finger gun' trick. Max insistently points out it's only a finger until the agent walks out in frustration. Max keeps plotting an escape, muttering "Come on, Smart, use that fantastic brain of yours!"

Tabletop RPG

Warhammer 40,000
- Baleful Eye -- a rare type of bionic eye with high-powered laser gun.

Western Animation

Inspector Gadget actually has a laser gun in one of his fingers but with all the other stuff he has in them it's no surprise that he can't seem to get it out when it would be useful rather than hilarious.
The Powerpuff Girls DYNAMO has finger missiles.

Real Life

There are novelty toy guns molded to look like fingers, which if held properly look as if the wielder is pointing with his or her own index finger. Technology does exist to integrate firearms into the fingers of prosthetic hands but the possibility does not seem to have been explored as the hands themselves are still being perfected.