Sure, grappling and punching is fun to watch. But in the brutal, no-holds-barred sport of MMA, there's nothing quite like a knockout. 

The combination of perfect timing and sheer physical force—plus the shock, awe, and surprise of getting slammed in the face—is almost an art form. (A very bloody one, at that.)

Scroll through the gallery for a look at some of the most astounding knockouts in MMA history.