Personally, I'm not a big fan of LANing in the game room at cons. Yeah, it can entertain a lot of people, but that means it takes up a lot of space. Generally I see cons being short on space and TVs in their game room in the first place.
I mean, one X Box with Halo is fine, but when you get two, three, or even four then you have 8, 12, or even 16 gamers sitting around playing the game. Just think of how much space that takes up. It would quickly monopolize the game room and alienate anyone who doesn't enjoy Halo/wants to play a game that's not Halo. It'd be like setting up four SSBM's.
As for requests - if I haven't said it already: King of Fighters: Maximum Impact. We ran a tourney for it at Ohayocon and it was a blast.