Fuck. Every band I listen to has some amazing guitar work in some form or another. To narrow this down would be impossible, so I'll stick more to the guys that shred.
DARKANE, THEORY IN PRACTICE, MORBID ANGEL, MR.BUNGLE (Trey fucking shreds), SOILWORK, IRON MAIDEN, TESTAMENT, MORDRED, SLAYER, EXODUS, IN FLAMES, PANTERA, NILE, CRYPTOPSY, DYING FETUS, EMPEROR...fuck. I could go on and on and on and....