What is Arm Cannon?
1.
Noun:
"...and so, with a final blast of his arm cannon, Megaman laid the diabolical Dr. Wily's latest mad creation to waste!"
2.
A video camera, usually a larger videocassette-carrying type.
Even though you don't use an arm cannon anymore, the copyright mafia can still confiscate your Coolpix camera even if you don't take any videos with it.
See