That's a white metal assault cannon. It's off a Land Speeder Tornado I think?
One of these:
I've got another few of those, and I've also got loads of multimeltas and heavy bolters kicking around, as well as a lascannon... I've made a nice multimelta/bolter combo which looks suitably SnazzGunn-ish for any spare
AOBR nobs I have after I've outfitted all the boyz squads with Nobs to lead them.
On the plasma cannon boy, the left arm is the normal chainsaw boy arm, with the chainsaw cut off above the hand and then the hand cut off at the wrist, drilled and pinned to get it rotated. It works really nicely as there's a bandage in just the right place there to hide the cut and it has a suitable handle for a big gun grip.
I couldn't have done either of these without my
GW Razor Saw, I was amazed by just how good it was, and how fine a cut you can do. For example, cutting off the top Rokkits on the Koptas, I've cut them on the first recess in the rokkit shape, and haven't damaged either of the resulting parts so the Rokkit tips will be used to convert something else.