These guys right here are my favorite. Mushroomhead is amazing, but an acquired taste.
2nd favorites:
System of a Down
Serj Tankian (Yes, he is the frontman for SOAD, but I'm talking about his solo works.)
Scars on Broadway (Practically half of SOAD, made up of the lead guitarist Daron Malakian, and drummer John Dolmayan.)
Dog Fashion Disco (Yes, yes.)
Hollywood Undead (HU Soldier 'till I die!)
Rammstein (and yes, I actually know what they are saying, I speak German.)
Oomph! (German band)
Voltaire (Cuban goth musician)
Other ones I like:
Basshunter (not really a band. >.<)
Buckethead
Capsule (Japanese techno / dance)
Dreamtheater
Eisbrecher (Another german band)
Eluveitie (Celtic metal)
Gravity Kills
KoRn
Limp Bizkit (Their newer albums suck.)
Modest Mouse (Amazing.)
Nine Inch Nails (Trent is an asshole, but his music is good.)
Rob Dougan
Rush
Supertramp
Styx
The Bloodhound Gang
Veil of Sorrow (Obscure swedish metal band)
And there's more, but I don't feel like listing. :D
I listen to a lot of music, because I play piano/keyboard, and do vocals. Sucks I can't find a band. >.<