Originally Posted by COBHCNick

I've seen a ton, so I'll just try to name the big ones.

Megadeth (4)
Children of Bodom (3)
Black Label Society (3)
Iron Maiden
Black Sabbath (2...One with Ozzy, one with Dio)
Iced Earth
Mastodon
In Flames (3)
Trivium (4...I dont even like them honestly. They always just open for bands I like)
GWAR (2)
Aerosmith (2)
Kiss
Shadows Fall
Rob Zombie
Amon Amarth
Exodus
Job For A Cowboy
Dream Theater
Seether (2)

Cant think of any more off the top of my head...