When a character has a gun that covers the arm, or a gun instead of an arm. Common in science fiction cyborgs.
Well known examples include Reiuji Utsuho from Touhou, Samus Aran of Metroid fame, Black Rock Shooter's eponymous character, and the various incarnations of Rockman from the Rockman series.
This tag implicates weapon (learn more).
The following tags implicate this tag: dual_arm_cannons (learn more).