I know you said rap, but check out System of a Down & Rage Against the Machine......Zach De La Rocha from rage always has a message with his shit and the guitarist is dope and pretty experimental, and if you happen to get into them then you'd like audioslave, which is the same band but minus zach de la rocha on vocals but with the guy from soundgarden doing more religious backed stuff....or you can go all out christian rock with creed :dead:
serj tanakian also has alot of potent stuff to say, but system of a down is a little heavy.
and nice andre 3000 refrence to whoever put that line up there.....you should really take it into account, stockton.....David Banner is one of the "good guys".....his lyrical ability may not be there, but he really knows what he's talking about and has pretty strong views from what I've heard in interviews as well as some songs.