Vocals is always hard for me to decide because I'm not very good at judging whether someone is a good vocalist. Like, I think Ozzy Osbourne and Dave Mustaine are good vocalists for their bands.
Guitars - Dimbag Darrell (RIP) of Pantera, Dave Mustaine of Megadeth Bass - Les Claypool Drums - hard one... Richard Christy (of Death's album The Sound of Perseverance), or Chris Adler of Lamb of God, or Ted Kirkpatrick of Tourniquet
If they all sounded good together that'd be cool. I don't know if they would of course.