Maynard James Keenan - Awesome singer, and his scream is killer. Chad Gray - Again, he can sing extremely well, but god his scream is powerful. Serj Tankien & Daron Malakian *cough* - I just heard a song that Daron did by himself on the new album. He's extremely talented, and he can fucking scream too, damn. And Serj is just a great singer and he does some odd things with his voice.
Cedric Bixler-Zavala (The Mars Volta) Robert Plant (Led Zeppelin) Freddy Mercury (Queen) Alicia Keys Branden Boyd (Incubus...especially live, his voice almost sounds better than on CD.) I will probably add more to my list when I remember.
Gerard Way-My Chemical Romance (pretty powerful voice) Chester Bennington-LP(") Kurt Cobain-Nirvana( nice sound)