Lots to choose from:

Eminem (post Eminem Show)
Usher (castrated at birth judging by his voice) [/MEAN]
50 Cent (if you get shot 9 times someone's trying to tell you something)
Will Smith I've never heard, I've only seen him in movies. He never seemed like he'd be much of a rapper, though.
Missy Elliot (saw her on Punk'd, she looks like a troll)
Beyonce (aka Bouncy)