I would have gone for Pete Rock, because the Soul Survivor album is just amazingly chilled out.
But, I went for other. My choice is QD3, and the strongest examples I can give of his laid back, smooth groove based production, are:
Tupac & Val Young - 2 Live & Die in LA
MC Eiht & Val Young - Thicker Than Water (this tune is just so fucking awesome)
Tupac - Heaven Ain't Hard To Find