10. A Perfect Circle
Though not technically a "supergroup," A Perfect Circle's various incarnations featured a who's who of the alt-rock world. Started by Tool guitar-tech Billy Howerdel and vocalist Maynard James Keenan, A Perfect Circle would draft such big names as Marilyn Manson bassist Jordie White (aka Twiggy), Queens of the Stone Age's Troy Van Leeuwen and Smashing Pumpkins guitarist James Iha. Though the band hasn't released new material in nearly six years, Keenan stated that they are working on a couple new songs that might soon see the light of day.