Well, assuming you mean "real" bands instead of soundtrack composers...
In no particular order:
Monster Magnet - From Silver Future to 4-Way Diablo, from Dig That Hole to Face Down, I do love me some Monster Magnet. Stoner Rock at its best: addictive riffs, crazy lyrics and something low, slow and heavy that feels just right.
KMFDM - Wait, did I say low, slow and heavy? My bad, let me just copy/paste that over here. Just look up the cover they did of Mini Mini Mini and you know what you're dealing with. From "Dirty" to "Save Me", they sure know how to bring the "ultra-heavy beat".
Korn - Yeah, yeah, I've heard it all. But you know what, I genuinely enjoy listening to songs like "A.D.I.D.A.S", "Twisted Transistor", "Cameltosis", "Make Me Bad" and "Got The Life". So, sue me.
System Of A Down - Sometimes hectic, sometimes bizarre, but always full of energy and downright enjoyable.
Rob Zombie - Even though his video clips are a epileptic's worst nightmare, the man still knows how to make music. His easy riffs, rough voice and countless shlock references have fueled many enjoyable tracks, from Pussy Liquor to Dragula, from Superbeast to Scum OF The Earth
Rammstein - Between Mutter and Mein Teil, what else is there to say? Well, perhaps that Amour is the best love song I have ever heard in my entire life. Seriously, just go listen to that song. Now.
The Prodigy - First they bring us hits like Smack My ***** Up, Spitfire, Breathe and Voodoo People. And then they go and reinvent themselves all over again with Invaders Must Die. Yes please.
Spineshank - I don't really know anything about this band... But I have their albums and I like what they do. Or did, more specifically.
Ill Niño - This and Linkin Park were the first bands to introduce me to the "heavier" side of music. Yes, I said Linkin Park.
Linkin Park & Eminem - Kind of cheating on this one. Two artists/bands I used to listen to over and over in the old days, but I haven't been following them in recent times. At all. However, I still put on their music from time to time. Partially out of nostalgia, partially because they really did make good music.
Part of me also wants to add Gorillaz to this list but... They've been letting me down a little bit more with each album they release. Their debut was great, even G-Sides had a few nice ones (Left Hand Suzuki Method for example). Then came the long awaited Demon Days, which was a little bit disappointing, mainly because it was a lot more mellow and a bit preachy - and I really didn't like the tracks Don't Get Lost In Heaven and the titular Demon Days. I never even listened to D-Sides. When Plastic Beach came around, the only track I actually liked was Rhinestone Eyes. I've listened to The Fall only once and I couldn't think of any track that I liked.
