Lesser known chess move like en passant. When you get into the ménage à trois board state you’re forced to immediately stop the game and eiffel tower with your opponent and any 3rd party. Whoever cums first loses.

I remember it randomly, but I think “oh, no I haven’t responded to this in so long, I can’t respond to it now” and agonize about it for the rest of time while still never responding or finally working up the courage to weeks or months later