A variation of the infamous Donkey Punch. While having anal sex with your partner, just before ejaculation, you grab their hair (or ears) with both hands and pull back hard to get a good whiplash. While pulling their head back, you thrust forward and headbutt them square in the back of the head hard. This results in the partner being knocked unconscious, but they will tighten up immensely, resulting in maximum pleasure.
(Note, this will hurt you as well, so this is only recommended to those manly men who can take a hit! Cheers!)
Greg: Hey, did you see Ryan? He's got a big cut on his forehead!
Joe: Dude, he Donkey Bashed his girlfriend last night!
Greg: No way! That's a true man right there