OH AND THE ACCUSATION GAME! Where you make an accusation and the person who posts below you has to answer for themselves guilty or innocent (or sometimes not guilty >.>)
Yes or no has a lot of different variations, like chocolate or vanilla?, or can you see a tree? (answered yes or no), and so forth. Kind of fun and great for learning about people.
And the cookie game. So the first post on a page generates a cookie, and the next posts all go back and fourth finding creative ways to steal said cookie. Then the last post on the page eats the cookie and the game starts over with a new cookie and another series of steals and so on c: