The one single band I would tour with it A Perfect Circle.
Maynard Keenan is one of, if not the best vocalist i've heard.
Others might be;
Tool
Pink Floyd, if they were to do a show with all the members...
Poison The Well
Metallica
And of course, Ozzy Osbourne.
I need to see a show of his before he stops touring or kicks...
He isn't even headlining OzzFest anymore.