In No Paticular Order:
Wu Tang Clan + all their solowork and the people associated with the Wu Tang.
Linkin Park + Fort Minor which is Mike Shinodas (the rapper) soloproject.
DJ Green Lantern, he doesnt make tracks all on his own, but he's my favourite music producer ever with the only possible exeption being RZA of the Wu.
Disturbed, no real comment, they make great music with high quality, having only ever made good albums IMO.
Deftones, I listen to them on and off, their emotional music I really love, its a great way to express feelings.
Jay-Z, I listened to him more before, and he's a bit to R&B/ P.Diddy style for me, but hes still a great MC, and since he's the CEO of Def Jam I have to include him.
Run DMC Great classical hiphop with high quallity and great flow.
Styles of Beyond Really GREAT underground hiphop/alternative group that makes very inspiring music and is also members of Fort Minor.
Korn What can I say? They created Nü Metal together with Deftones and is a great band all in all.
Tupac The rolemodel for many, and probably on of the best MC's of all time. Has got many great tracks that even many nonhiphopers like. He was great at making other people understand the hiphop culture and accept it. The war against Biggie Smalls didnt help though.
Thats what I came up with at the moment.