In that the distinctive trait is more it's uniqueness rather than simply its range or ability to convey an emotion.

Even guys like Lil' Wayne, who may have one of the few voices that I don't like, has an immediately recognizable voice.

But some voices that I do like:

Chuck D, Black Thought, Kendrick (because it's distinctive), GURU (obviously), Grand Puba, Q-Tip, Xzibit, Andre 3K, T-Mo, Dr. Dre, Snoop, RBX, Kurupt, Luda, KRS, Roots Manuva, Pac, Cube, DOC, BIG, Common, Fatlip, Method Man, Ghostface, CL Smooth, LL, Lauryn, Queen Latifah, Ice T, Both MC's from Camp Lo, Mos, Greg Nice, Lupe, Dilla, Pun, Del, Dave from De la, Zach de la Rocha, Royce, Phonte, Freddie Gibbs