A.O.T.P. I know its a group, but in general, all of their music is awesome. Vinnie Paz, Celph Titled, Demoz, Crypt, Reef, King Syze, Planetary, etc
Snoop Dog and Dr. Dre, for the sake of the good old times, since the rest is, unfortunately, dead. However i prefer their old works, not these recently.
Wiz Khalifa. Yeah, lots of Wiz groupies nowadays, but his music is good to chill, not like those bling-bling songs which only talk about money, ferraris and shit. To be honest, at the beginning i didn't like him much but i started listening his songs with more attention and i actually enjoy them a lot. He has the ''new guy'' stereotype, because he appeared out of nowhere and is making huge success, but he is actually very good.
Eminem of course. He is a classic, tough i think sometimes he exaggerates on his musics. Yeah, his childhood and life were hard but.. it gets too depressing sometime.
Westside Connection. Another group i enjoy in general, also, Ice Cube, nuff said.
Cipress Hill. I wouldn't put them exactly on the top but.. still like them more than most other rappers. Also Delinquent Habits, Kid Cudi, Talib Kweli, Mos Def, Juelz Santana, Warren G, Scarface, Lauryn Hill, Masta Ace, Black Moon, , Common (beef with Westside Connection xD), list goes on O__O
I dislike those Lil Wayne, Drakes, Souldja Boys and a couple of those new rappers >_>. Still playing with auto-tune, wtf.
From the deceased rappers, i enjoy Big L, Big Pun, Tupac, Eazy E (San andreas Ryder ftw xd), Nate Dogg and i'm sure i'm missing a lot of people who i can't remind atm.