Maynard is my fav...just something about his voice, it kinda blends really good aspects of both genders; the power is there, but he can also sing very softly yet keep you on the edge, hanging on the notes. I agree that Patton is extremely talented, but some of his stuff is a little too out there for me. Hetfield's stuff on ...And Justice is awesome, wish he hadn't converted to southern rock. This thread so far has been mostly metal singers, but I think Sarah McLachlan has a beautiful voice, very full of emotion, granted the majority of her music is really poppy.
I dislike Labrie...I don't think he's a bad singer, I just don't like the sound of his voice. I always wonder what DT would have been had they found somebody besides him. Who knows, could have been great, could have been not so great. Also, the guys who sing for Linkin Park suck balls, talk about whine whine whine, then the other guy trys to be hardcore with his rap = shitty.
Also, I hate Nickelback...for no specific reasons...I just think they suck, just thought I'd throw that in there