Answer:
Nevermores Jeff Loomis
Dream Theaters John Petrucci
Deftones
Wes Borland of Limp Bizkit used a 7 string for most of his early career with the band.
Korns Munky
Soulflys guitarist has a signature Stealth (BC Rich)
Triumphant Return
Slayers Kerry king
Rusty Cooley uses 7 string guitars
Steve Vai
Fear Factorys guitarist does
Cannibal Corpse
Flaw
Unearth
Kritic Kill
Periphery
Muse used a 7 string for their song Citizen Erased