I'm not sure if this was mentioned but Dr.Octagon is actually Kool Keith. He's one of my favorite MC's, and has a few diffrent personas. His style is so original and he's always ahead of his time.
Supernatural is the best freestyler I've ever seen, I have a cd of all freestyles that battles, small radio spots and one off recording sessions. In one battle in the middle of destroying his poor competition he says something about B.I.G. comming back and starts doing biggie's voice. It's fucking creepy, he sounds almost exactly like him when he does it. In small freestyle session he rhymes from the perspective of all the X-Men.
Onyx
Jedi Mind Tricks
Cage
MF Doom (wears a Dr.Doom mask when he raps, pretty fun to see.)
Gang Starr
