I'm gonna have to go with my man Holocaust. I was thinking about him when I came up with the idea for this thread.
Dude is just a total mystery to me. I have no idea what his deal is. I would think he's either insane or just totally fucked up on drugs, or both, but then he appears to be leading a pretty normal life, and interacting with people as a normal person would. I just can't figure him out.
Then there's people like E-40, who has a very unique (and awful) style of delivery, but he's still just rapping about the same ol' shit.
I guess ODB was quite unique too, before a lot of people started biting his style.