Some peeps were sharing stories of video game dickery at a certain place online, and while most were so-so, this one managed to class up the joint:
In an online 8 player free-for-all in Age of Empires 2 I secretly made separate alliances with every player, then got them all to give me some resources to build a wonder so that we could win a team victory.
Wonder built, I waited until the victory timer was at about 15 seconds, and then broadcast to all "The Lannisters send their regards." and de-allied them. I alone won and they were defeated.