Starting with the obligatory XKCD http://xkcd.com/763/ Goldeneye- facility level. I would wait for the scientist to appear in the toilets to get the keycard... given that was the level that also gave one of the best cheats (invincibility) it always seemed the time limit there was really harsh. Rainbow six vegas- after not playing it for several months and it being the middle of July and friend and I decided to replay it. We had forgotten about cover (some games use cover, this revolves around it).... Soul calibur- I almost never block, same applies to most fighting games actually. Made it nice when I got the bonus sword that could not block but had amazing offence. That would be the sort of thing I am going for but if you really want to share the "I learned game theory, disassembled the game to learn the algorithms to generate the perfect play and built a controller input with an arduino to play the game for me" style answers that works too. Where "I learned to snake in mario kart" falls I leave to you to decide. Also feel free to include some board games, card games and such like.