Its Mike Patton, legend of rock and music in general, and seriously underrated imo. I was looking for a nice photo and found this one with the megaphone, and what could be better for a forum avatar?
If you don't know Patton, as well as leading Faith No More and many other bands, in terms of games, he 'voiced' the anger sphere (Part of Glados in Portal), and many of the infected in both Left 4 Dead games.
What impressed me is the sheer range, he can swap from growling death metal to lounge music crooning in the blink of an eye, and has put his skills to just about every genre going.