Why'd you make this a poll? There are too many models to choose from. My favorite are the basic kroot. Tons of stuff to put on them, very unique appearance, and they actually look like they'd eat you
Plus it's the only unit that I've made a conversion to in my small time as a 40K player. My shaper has a pulse carbine and the butt end of a kroot rifle as a close combat weapon (looks like a sickle now). He's holding the carbine at his side and the rifle end diagonally across his chest, but close to his throat, so that he's doing the "I'm gonna slit your throat" motion. I haven't painted it (or much of anything) yet.
Poll
