Obligatory GOATs: of course everyone loves Tupac, Biggie, Eminem, Nas, and older school stuff Wu Tang (especially Ghostface and GZA), Big L, NWA, Run DMC, Eric B. and Rakim, Public Enemy, ect.
Besides them I love MF Doom, Aesop Rock, Lyrics Born, Gangstarr (RIP Guru), Jedi Mind Tricks, E-40...