What I always thought would be grand would be to make sort of a playable chat room. Have it so that the user could select a Mario character or something, and then it would be sort of like a game, where everybody else in the room is represented there, and you can hear anybody nearby... Sort of like a massive online game, but not oriented to that point (they're hard to make.)
Then there'd be a lot of pointless things to add, such as the pointless environment, character expressions with macroes, etc...
...
Oh well... there never seems to be enough time to make that sort of thing. But it still would be grand.
Go Moon!