Harker

Gunnery Sargent Harker.

He's a heavy bolter that can move and fire.

Big woop. His real reason for existing is to stick his ass with some Veterans in the back and hold your objective while putting some heavy bolter fire into the enemy (never a bad thing).

See, all that matters is he has infiltrate (so he goes down last) and has Stealth for a 3+ or 2+ cover save.

Handy for foot armies that want a solid troop to sit on an objective and (hopefully) not die. Having 2 meltaguns available for point blank defense is of course a nice touch, on top of the two heavy bolters you should be giving his squad.

I'd only take him in this instance, he's not worth it in other army types.