I was looking to add a little "game" to my boards, and all I could find along those lines was the Q&A game.
I was thinking a Janken (rock paper scissors) hack would be great.
For example, someone starts a game topic, and in addition to whatever text they enter they also select one of the three. It is not displayed, however, until someone replies with their own selection. Then both are revealed and results are listed.
I was hunting down a ROM of one of my childhood favorite games - Alex Kidd - when I came up with this. Anyone who ever had a Sega Master system will know what I have in mind.