My own added onto the list:
[Assassin's Creed (at the very least, 1 and 2)] -- Train my guards that, if their colleague suddenly collapses with a small knife planted in his back, the still-living guard will not just say "Somebody there?" and then fail to actually look anywhere for the assassin that's standing in the shadows.
[Deus Ex: HR] -- I would train my mercenaries not to simply punch a guy in the stomach and leave him bleeding, so that he can become a God of machine-powered-destruction, but actually SHOOT HIM.
[Oblivion/Skyrim] -- If I were a bandit chief, I would tell my bandits, that when they see the Dohvikiin, saviour of Skyrim, protector of the Nords, banisher of Alduin and pretty much a whole new Divine, NOT to go ask him/her for 'your money or your life'....FUS...RO...DAH!
