Player Affix of the Tichondrius server has figured out a way for her and a guildmate to use an empty tab in their Guild Bank to play checkers. As you can see from the image above, one player is Arcane Dust and the other is Netherweave, but any two distinct items could work.
Admittedly, one row is missing and there are too many rows across, but a game could still reasonably be played. It's no musical chairs in Karazhan or pet wars or even downtime games, but it is pretty ingenious.
EDIT: This is what I get for posting while out of town, double-post!