Pretty much any fight scene with Tony Jaa in "The Protector" (also known as "Ong bak 2" and "Tom yum goong"). The shear violence and impact of some of the stuff the guy can pull off is unreal. Anyone who's seen it knows how crazy he gets with his flying knees of death.
Also, the final fight with him breaking the legs and arms of about 50 henchmen in pure zenned out methodical rage is completely and totally insane, yet highly satisfying.
It's an ok movie at best, but one of the few worth seeing for the fight scenes alone.