Originally Posted by: jamesplaysgitarpshaw turkey.
noone is heavier than system of a down.
MAYBE nile...

Wow man, there are a hell of a lot of other bands that have tones that are so far beyond that in terms of heaviness (just refering to the power of guitar tone):

Entombed ('Left Hand Path' cd) - the heaviest and nastiest death metal tone ever, downtuned with massive levels level of distortion (sounds like an overdrive pedal onfront of distortion unit on front of a large Mesa rig through a wall of 4x12 cabs compressed to the point where the palm muting is on the verge of rupturing stereo speakers). Also, it sounds like everything is downtuned to C or even B off regular 6 string guitars so you can actually hear the strings flopping about and hitting off the pickups! Very original guitar sound, still havent heard it replicated anywhere else.

Meshugga - The latest offering has a guitar sounds that really attacks stereo speakers - very thick and very powerfull, plus it has the added power of being played off downtuned 8 string guitars (low A). That plus the production is amazing - check it out, the pollyrhythms, weird tempos and mathmatical approach to riffing is not for everyone but the tone is crazy heavy.

Some others worth mentioning, Prong, Helmet, Exodus, Darkane and a whole load of others. Check em out for the tones!