I like the idea of simple games that give players a lot of flexibility in strategy, like Prisoner's Dilemma, but something people would actually play for fun. So far, I've managed to find Pass the Pigs, a dice game, and Dominion, a card game. What other games have endless strategies to try out, yet involve really simple rulesets?
Sorry if this is off-topic. I didn't know where else to post this.