but my actual favourite isn't explained super well here and I wouldn't have known what it was had I not recognised it. it's the tic-tac-toe one.

iirc it was an attempt to make the best tic-tac-toe AI, but to make it non trivial they put it on an infinite playing field since that hasn't been solved. One of the AIs was a learning AI, and it figured out that if it made its starting move extremely far away from the starting point, the other computer would try to render a massive playing field, run out of memory before it loaded, crash, and then the timeout would be considered a victory.