Erm, non-mainstream rap.

[EddBundy]

Aesop is OK nothing too special.
Like JonG said, ICP and Family Force are not rap or mainstream.
Mainstream rappers i like, Jay-Z, Kanye people like that when it comes to mainstream.
Un-Mainstream, probably JakProgresso, Moongod Allah, Rhyme Asylum and La Coka Nostra.