A game where a group of people sit around a table with a coin, preferably £1, but most/any will work. One player spins it for the person on their left to catch between their index and middle fingers. Play moves in a clockwise direction. If the spinner mis-spins it 3 times, the catcher slides it along the table very quickly at their knuckles. This also happens if the catcher catches it with the coin horizontal. This happens in reverse if the catcher mis-catches it (once).
We played knuckles in school today, and people were wondering why our knuckles were all mashed up.