Probot

The all-star metal project of Dave Grohl where he played almost all the instruments (outside of lead parts by Bubba Dupree of Void, Kim Thayil formerly of Soundgarden, and bass parts by lemmy) that featured a multitude of vocalists. Dave recorded tracks reminiscent of the singers' respective bands, which he grew up greatly admiring, and sent the recordings to them, with a note stating simply "Send back with vocals."

Complete list of singers
Cronos (Venom)
Max Cavalera (Soulfly, Nailbomb, Sepultura, Cavalera Conspiracy)
Lemmy Kilmister (Motörhead)
Mike Dean (Corrosion of Conformity)
Kurt Brecht (D.R.I.)
Lee Dorrian (Cathedral, Napalm Death)
Scott 'Wino' Weinrich (Saint Vitus, The Obsessed, Spirit Caravan, The Hidden Hand)
Tom Gabriel Fischer (Apollyon Sun, Celtic Frost)
Snake (Voivod)
Eric Wagner (Trouble)
King Diamond (King Diamond, Mercyful Fate)
and Jack Black (Tenacious D)