My favorite rapper of all time would have to be DMX. Gets me pumped for the gym. I also recommend: Rakim Gang Starr 50 Cent Snoop Dogg (Back in the day; new stuff sucks.) The Game The list goes on...
The new album by The Roots is amazing. I haven't finished listening to it yet, but it is great so far. They went back to their "roots". Much better than the past couple albums they put out. Has the feel of Illadelph Halflife and Things Fall Apart, just slightly more refined.
http://www.youtube.com/watch?v=25e1Qc17wlY Far East Movement - Fetish. Digging this one a lot at the moment...