Deftones are underrated. They didn't deserve the nu-metal flak, because they were kind of like, post-rock vs. metal. Post-metal, I suppose. This massive, sweeping, throbbing noise. They were much more interesting than most of the nu-metal bands.
American Head Charge, I have the first album and it's far too long, but it's pretty fucking brilliant.
Fear Factory have some good tunes, Mushroomhead too (they did the masks/face paint thing before Slipknot, but then somebody whose name escapes me, maybe The Residents, was doing it long before then).
Incubus are such a woefully misunderstood band. They have a big radio hit with a boring acoustic ballad, and suddenly everyone loves that tune and thinks they're easy listening. Some of the earlier stuff like 'Certain Shade Of Green' is pretty heavy, and pointless cussing aside 'Megalomaniac' is a hell of a tune. In fact they have some pretty decent albums.