Technical Death Metal. Depending of the band you get this ridiculously crazy and sophisticated instrumentalism and polyrhythmic beats like Archspire, other times you get more progressive, experimental groups like Blood Incantation that mix and match genres and soundscapes.
In fact, the newest album from Blood Incantation is a good example of that, one moment you're listening to fast blast beats and then it suddenly takes a hard turn into pink floyd and slowly starts crescendoing back into fast Death Metal over the next couple of minutes. It's an absurd aural experience to say the least, but I really like experimental music that pushes boundaries even when it doesn't totally work.