(Pertaining to the classic videogame Super Smash Bros.) When Donkey Kong unleashes his maximum power punch in the face of an opponent.

Pathetic urban myth about anal sex and misogynist violence made up by virgins who don't get laid much. Besides being medically impossible (read a biology book folks, knocking someone out doesn't cause that effect), any gay male will tell you that smacking someone who you are having sex with will lead to you getting beaten to a pulp.

Donkey punching is more safe and effective when you use a swift but controlled open-handed karate chop to the very base of the skull, near its insertion on the neck. I believe this stimulates nerves that contract the anal sphincter muscles.
The legal definition should be removed because the goal is not to make the recipient unconscious. Also, this is not something that people actually do, its a freaken joke, you feminazi.
But, if you were to do it, a donkey punch to the spine just above the ass would probably work better (and provoke fewer lawsuits) than a blow to the head, which might even relax the anus. This is because sacral nerve stimulation has been linked to sphincter contraction (in cats)- dont ask.
Now, if you really want to get some sphincter contraction, without the whole punching thing, you cover the recipient's nose and mouth with a hankerchief full of ground pepper or something that will make her cough (or just ask her to cough repeatedly). Coughing tightens the anus twice as much as voluntarily squeezing.

The melee attack with the plasma pistol in Halo 2.

Man of chivalry and honor, immediately precedent to Don Quixote in the fonetic fon book.

A sandwich at Chicago Bagel Authority. It is a bialy with chicken salad, BBQ sauce and smoked cheddar on it.

The act of using a charged plasma pistol followed by a melee attack in the video game Halo2