Basically, you choose odds or evens and remark "Once, twice, three, SHOOT!" each player either holds out a closed fist, 1 finger, or 2 fingers, therefore the total can either add up to 0, 1, 2, 3, or 4. If it is 0, no player wins. If it is even (2,4) the evens player wins and if it's odd (1,3) the odds player wins.

Briefly, "the realization that each random passerby is living a life as vivid and complex as your own." Originally from the Dictionary of Obscure Sorrows, which has a lot more beautiful neologism definitions like this you might enjoy.