Appendages (firearm) – The ability to turn an appendage into a firearm.
Bushwacker (Marvel) can turn his right arm into a firearm (Official Handbook of the Marvel Universe V3 #1.
Sniper (Valiant) has this power in both arms (X-O Manowar #3).
Bodycount can turn his arms into firearms and other objects in the Savage Dragon Universe.
Gunman appears to have replaced his hands with firearms in the Savage Dragon Universe.
Tyr (DC) has replaced one of his arms with a blaster cannon.
KGBeast (DC) – Who’s Who Update ’88 #2
N.I.L.8 alias Eric Marr has a gun for an arm in Magog #12 (DC).