MF DOOM

"Found a way to smash a triangle though the circle shape" - MF DOOM

MF DOOM is a rapper, not a superhero, but he has been wearing a mask for the last 20 years. When I think of of masks or helmets, DOOM's mask always comes to mind.

@Mike Rogers is right. DOOM's mask is very similiar to @Matt Scribner's gladiator helmet.