Remember those old text adventure games from the 80s, like Zork and Leather Goddesses of Phobos and Planetfall and Lurking Horror? I loved them, and I loved how they engaged my imagination while they encouraged me to solve puzzles.
When I was at Origins, I saw this game called JUNGLE ADVENTURE, which uses a system called Parsely. It's essentially a live version of the old text adventure games. A GM plays the part of the computer, reading descriptions and giving responses to a group of any number of players who are trying to solve the adventure.
I haven't played it at a con, yet, but I've read stories from people who played it in a room of a hundred or more people, with delightful and hilarious results.
I've had such a good time reading JUNGLE ADVENTURE and SPACE STATION, I went to RPGnow and bought ACTION CASTLE, the very first game that was released using this game engine. (Note: I didn't realize, until I started writing this post, that mementomori sells the games directly, so I've linked to those pages here; shut up and give them your money!)
I'm not entirely sure it would work on Tabletop, but I'm going to try it with my friends at our next game day.
I'm just going to throw this out there: I bet it would be really easy to design your own games using this system… get excited and make something, Internet!!