didnt really read the rest of the posts but i think mickeal (sp?) from opeth and randy of lamb of god are two of the most talented metal singers, for non metal i like mike patton because he can pull off almost any singing style well.
Maynard [James] Keenan (of Tool / A Perfect Circle)
Jeremy Engik (of Sunny Day Real Estate / The Fire theft)
Chris Simpson (of Mineral / The Gloria Record)
John Lennon