Rap mostly and I don't really have a favorite I think the list may actually be shorter for those I dislike. But for anyone interested I enjoy:
RA the Ruggedman, Ill Bill Army of the Pharaohs, Jurassic 5, Wu Tang, Pace Won, Papoose, Chris Webby, George Watsky, Eyedea, Aesop Rock, Atmosphere, Brother Ali, Sage Francis, Intuition, Soul Khan, Eminem, Prince EA, Immortal Technique, Spose, Lupe Fiasco, B.O.B, Kid Cudi, Cage(early years), Gangstarr, Canibus(earlier stuff), Big L, Big Pun, Pac, Jay Electronica, Murs, Hilltop Hoods, Bliss & Eso, Grieves. I now there's more I'm forgetting but that's some of what I've been on lately.
Rock I like a wide variety but mostly alternative from the 90's as that's what I grew up with:
Offspring, Sum 41, Primus, Presidents of the United States, Rage against the machine, Cage the Elephant, Sublime.