I'm looking some raw, mayhem inducing guitar riffs that aren't speed metal. Not necessarily slow tempo, but slow enough to stand out. A few examples:

Pantera - Walk
Slayer - Seasons in the Abyss
Living Color - Cult of Personality
Atreyu - Becoming the Bull

Please, no Metallica. They have achieved the sound in a few songs but most of their stuff is more polished than what I'm looking for.