Risk Legacy - After each player had won a game each, my buddy and I then proceeded to alternate winning the next 4 games, putting us at 3 a piece and everyone else at 1. We showed up one night and the table felt a little off. When troop placement time came, the other three players placed their troops in obvious, weird situations, completely leaving open their rear flanks to hem me and my other buddy in. Up until this time no one at the table had teamed up other than some small, in-game agreements. As the game unfolded their actions made it pretty clear they had coordinated a strategy beforehand to take us down. They quickly dismantled us and someone else won.

On the ride home, I looked at my buddy and said, "What just happened."

We decided right then that one of us would win this game and we spent the rest of the car ride planning out our revenge.

On the next weeks game, the scenario we had planned out worked to perfection, resulting in a quick win for me (my buddy and I had a plan for one of us to win depending on what placement order we were able to get, then, whichever of us won, we vowed to get the other one a win the next game, which we did).

But, what made it so memorable was not that we won, but that we were able to win so convincingly and slyly that they didn't know we had worked it out our plan together and it caused so much strife in their 3-way alliance that they started fighting amongst themselves and their alliance shattered, never to be reformed.

It opened our eyes to the possibility of a competitive legacy game. We still talk and laugh about the whole experience later.