The power to
generate firearms and/or projectile weapons from one's own body. Sub-power of Weapon Transformation. Variation of Natural Weaponry and Weapon Manipulation.
User can transform themselves or parts of themselves (arms, legs, shoulders, etc.) into strong gun-like weapons with massive fire power. One can actually
control the movements of such gun-like weapons when fired from both hands at high speeds, displaying a huge amount of destructive power. The possessor of this ability can make the projectiles from their (possibly numerous) equipped arsenal change direction, curve, bend, twist, travel and fly longer distances, lock onto targets and automatically follow targets with perfect precision and accuracy.
Though user often manifest the firearms from their arms and hands, it is not entirely uncommon for the user to be able to manifest said firearms from other parts of their bodies, such as the legs, head, or chest.
Gun may get jammed.
Need to reload up to hundreds and thousands of rounds of ammo.
Arm Cannon (Astro Boy)
After being "improved" by Dr. Stylish, Seryu (Akame ga Kill) had guns hidden in her arms and even her mouth.
Mercenary Tao (Dragon Ball) disconnects his right hand to reveal an arm cannon, from which he fires his
Super Dodon Wave.
Dr. Kochin's (Dragon Ball Z: The World's Strongest) machine gun arm.
Super 17 (Dragon Ball GT) using his
Hell's Storm attack.
Allen Walker (D.Gray-man) using
Cross Paling, which morphs his arm into an energy cannon.
Level 1 Akuma (D.Gray-Man) can create a large amount of guns on their bodies (not exactly their arms, per say).
A Level 4 Akuma (D.Gray-man) turning its arms into Gatling guns that fires deadly
Dark Matter blood bullets.
Albert Heinrich/Cyborg 004 (Cyborg 009) possesses a fully functional gun barrels in his right hand and rocket launchers in his legs.
Bald (Fullmetal Alchemist) possesses a double-barreled rifle in his automail arm.
Franky's (One Piece)
Weapons Left is a multi-barreled machine gun that can pop out of his wrist.
...and the upgraded version house in his knuckles.
Baby 5 (One Piece) ate the Weapon Weapon no Mi, which allows her to turn any part of her body into a weapon - including guns.
Franklin (Hunter x Hunter) morphing his fingers into guns to fire
Ganzu Ragyuuru spell generates turrets from Rodeaux's (Zatch Bell!) wings
Ginkotsu (InuYasha) has a cannon built into his shoulder.
Goryumaru (InuYasha) possesses a cannon-like demonic arm that fires lasers.
Kujiranami Hyōgo (Rurouni Kenshin) replaced his missing right hand with an Armstrong Cannon.
Unit 1 Guyver (Guyver) using the
Mega-Smasher, a powerful particle beam cannon in its chest.
Yao Cannon Lord Yao (Dragon Ball GT: A Hero's Legacy) demonstrates.
Slot Machine (Yu-Gi-Oh!) features a Plasma Laser Cannon on its right arm.
Genesect (Pokémon) is armed with a cannon, which allows it to fire its Techno Blast, a powerful artillery attack dependent on the drive installed.
Umibozu (Gintama) replaced both his lost arms with mechanical prosthetic that can change into guns.
Vash the Stampede's (Trigun)
...and his cybernetic replacement, which also conceals an integrated firearm.
Halloween (Marchen Awakens Romance) has a Weapon ÄRM called Napalm Death which brings a cannon out of his back. The cannon shoots out concentrated flames and each shot is stronger than the one before.
Bunnie D'Coolette (Archie's Sonic the Hedgehog) utilizes her arm cannon.
Badnik Amy (Sonic the Comic) had machine gun-esque crossbows mounted on her wrists
Commander Brutus (Sonic the Comic) has a raygun in place of a right hand...
...which he uses on Robotnik.
Ultimate Humungousaur's (Ben 10: Omniverse) bio-missile launcher/gatling gun.
As the Ultimate Spider-Slayer, Alistaire Smythe (Spider-Man: The Animated Series) possesses organic laser guns mounted on each shoulder.
Arsenal's laser arm (Young Justice: Invasion)
Cyborg's (Teen Titans) Sonic Cannon.
Destructor (Futurama) has a Gatling gun installed in his right arm.
After losing his left hand, Blade (Marvel Comics) used his S.H.I.E.L.D. connections to replace it with a prosthetic gun.
The Engineer (Wildstorm/DC Comics)
Bush Whacker (Marvel Comics)
Yang Xiao Long (RWBY) possesses a gun built into her cybernetic arm.
Mercury Black (RWBY) firing his gun leg.
Metal Sonic (Sonic the Hedgehog/Archie Comics) has a plasma cannon in place of a left hand.
The Metallikats (Swat Kats: The Radical Squadron)
Agent Venom (Ultimate Spider-Man) sprouting twin missile launchers from his shoulders.
A Steel Clan robot (Gargoyles) aims its arm cannon.
Tiger Claw (Teenage Mutant Ninja Turtles 2012) brandishing a cybernetic raygun arm.
Metamorphia (Sonic the Comic) turns her left arm into a raygun to attack Shortfuse.
Shortfuse the Cybernik (Sonic the Comic) firing his wrist-mounted laser gun.
The Hidden Gun (Assassin's Creed) was an arm-mounted weapon invented by Altaïr Ibn-La'Ahad.
Emperor Calus (Destiny) possesses a Gun Arm that fires off powerful projectiles.
Eis Shenron (Dragon Ball GT) performs his
Dragon Ball Blast, in which he converts his left hand into an energy cannon.
Barret Wallace (Compilation of Final Fantasy VII)
Duon's (Super Smash Bros. Brawl.) pink side fires powerful blue and purple lasers
Barrett (Mega Man Legends 3)
Bass' (Mega Man Classic) Bass Buster
Gray Fox (Metal Gear) using his arm cannon.
Ash Williams (Evil Dead: A Fistful of Boomstickmaking) makes use of his arm-mounted gatling gun.
Gear REX (Metal Gear Solid: Peace Walker) has a gun-like protuberance that shoots acid.
Mega Man (Mega Man Classic) using his famous
Mega Man Volnutt (Mega Man Legends)
Jolly Roger (Pirates of the Caribbean) has a pistol-like weapon for a right hand.
Mecha Bandicoot (Crash Twinsanity) has a rocket launcher for a right hand and a plasma cannon for a nose.
Turbo Mecha Sonic (Super Mario Bros. Z) possesses a retractable machine gun in his arm...
...which can convert into a missile launcher.
Zero (Megaman X series) with his Z-buster.
The Arm Cannon is Samus Aran's (Metroid) primary weapon
After using the power of the Tablet of Order and Chaos, Hammerhead Noir's (Spider-Man: Shattered Dimensions) Vulcan machine gun and a missile launcher fused to his arms.
Grobyc (Chrono Cross) with the forbidden arm cannon
A Mii Gunner's (SSB4) arm cannon can fire a variety of projectiles and types of energy.