I'm pulling for Touhou Sky Arena. It's a 3D free-flight fighting game for 1-4 players (of course, set up for a convention it makes more sense to do 2-4 players).
I've been in two Sky Arena tournaments, and they're a lot of fun. I've heard it's not on the official tourney list, but if there's a couple stations, a couple hours and some people willing to duke it out, I can run an unofficial tournament. The winner(s) can try to take me on, for my stash of past prizes (if I win, I'll add some trinket to it- the more to wager at the next convention).
I'll be posting info about the game in a separate thread, be sure to check it out!