The Palladium! I saw System of a Down and the Red Hot Chili Peppers there a few years ago... AWESOME venue! It's like watching a big band in a high school auditorium.
I also really like both the House of Blues in Anaheim and on Sunset. There is always a cool vibe there, and major bands/groups play there often. I've seen a few metal bands at those venues... epic!
I like House of Blues a lot (Sunset one is only one I've been.) Nice place, relatively small venue that gets some good acts. So just get there a bit early, and you will be very close to the stage for the show.