Michael Pissping is the number 1 person that comes to mind. The most obvious thing in the front of my mind is when Rivera was on step 9.5 of the 10 steps to a sweep into mount and Piss grabs the fence and holds on for dear life. That's not the only time, just about every time he fights, well..., most times, I see him do something and I think to myself, "How the **** does the ref not penalize him!?"
However, a more blatant dirty fighter is Cheick Kongo. He doesn't even try to hide the fact that he is trying to be a one man sterilization machine. Kos, just because he's a shitty actor. I'd have to put Matt Hughes in the same boat as Kosdick. I don't know how many times I've seen Hughes jump to the ground holding his package after a leg kick had clearly landed to the thigh. I'm not sure who it was, Matt Serra I think, had landed an obvious outside legkick, not inside to the thigh, but outside to the hip, and Hughes didn't just fall down, he ******* jumped to the ground holding his package.