I think I have it down to one riff: the intro (first one or two minutes) to the Art of Dying by Gojira. Not my favorite band but a wicked riff.
10/18 - King Diamond
10/24 - Pallbearer
11/01 - Suffocation
11/30 - Devin Townsend
12/06 - Distant Worlds: the Music of Final Fantasy