I've always loved underground rap like Mr. Lif, Aesop Rock, Dr. Octagon, Lyrics Born, Blackalicious, and of course the supervillain himself MF DOOM to name some of the bigger names.

Honestly, the mainstream rap that's released these days seems so shallow compared to their underground peers. To me, without the thought of making a "hit" in their minds, underground MC's and producers tend to be more imaginative and are willing to take more creative license in their sound.