lil' wayne, in saying this i know I'll catch a lot of flack but for some reason i cant get enough of that dudes voice, its not his lyrics or his content or him. I don't really know why either.
jason mraz, if you've ever seen him in concert and heard him bust into 10 minutes of operatic singing in the middle of a song you may agree.
johnny cash
bob dylan
muddy waters
are just a few of my favorites.