Well, I would have a heavy metal band, so...
Vox: Ozzy (Black Sabbath, solo artist)
- He's just too
fucking metal! to leave out.
Lead Guitar: Janick Gers (Iron Maiden - interchangeable with Adrian Smith or Dave Murray, based on my mood, I guess

)
- A metal band without an Iron Maiden guitarist? Impossible, I think.
Rhythm Guitar: Jesper Stromblad (In Flames)
- His rhythm licks add beauty to In Flames' songs - therefore, he makes my dream band.
Bass: Cliff Burton (Metallica)
- The greatest metal bassist. Ever. Would get Anesthesia (Pulling Teeth) to play at every gig.
Drums: Dave Grohl (Foo Fighters, Nirvana)
- No contest, probably. More rock than metal, but far too awesome to leave out.
Extra peoples:
Guest vocals: David Draiman (Disturbed)
Guest Lead: Randy Rhodes (Ozzy Osbourne), Jim Root (Slipknot, Stone Sour)
Guest Rhythm: James Hetfield (Metallica), Dave Mustaine (Megadeth)