There are a lot of channels on Youtube devoted to guitar covers, but one of my favorite's is Elena Verrier, who specializes in absolutely tearing up metal tracks.
Metallica, "Blackened"
"Resident Evil 3 Save Room"
Death, "Spiritual Healing"
Slayer, "Dead Skin Mask"
Nile, "Permitting the Noble Dead to Descend to the Underworld"