Experimental Metal.

Thanatoschizo - Schizo Level (Their other albums suck for the most part, but Schizo Level kicks ass)

Quest for Blood - Self Titled
(Might also be called Quest For Blood With Yukihiro Isso)
 
Gorguts, Spawn of Possession, Behold...The Arctopus, Electrocution 250 (Metal and Cartoon music, what's not to like?), anything with Ron Jarzombek in it, Gory Blister.
 
I don't know if I'd say all of these are "experimental" but these albums have many an odd riff and abstract passage.

Gorguts - Obscura
Adramelech - Psychostasia
Demilich - Nespithe
Blut Aus Nord - The Work Which Transforms God (has a slight industrial touch)
Carbonized - Disharmonization (I'm not even sure if I like this but it's the definition of "experimental")