K21

My first impression is some kind of particle beam launcher, with a really high-powered battery (the "K21" piece on the back) to power the rest of it. Basically your average "man-portable positron collider" type of thing, designed to send a steady stream of near-lightspeed protons or positrons out the business end to chew through _really_ tough armor. Of course, if you wanted to get really exotic, it could launch packets of antimatter held inside magnetic bottles or something equally nasty (tiny black holes? naaw, too impractical).

(I get the feeling I should lay off the Masamune Shirow stuff for a while...)

Seriously, it screams "This is a BFG so badass that I have to wear powered armor just to protect me from the nastiness it shoots at you". Probably heavy as all get out, but knocks holes big enough to drive cargo lorries through into its targets.

Did I mention that it's a cool drawing?