Tic-Tac-Toe is kinda boring for me since it's always a tie game with me.
To keep it on topic with theme parks, my friends and I always play "number tic-tac-toe" while waiting in lines... You know, the one where you only say numbers and you have to memorize who's gone where...
See:
123
456
789
Those are the numbers, and it should be pretty obvious. It's actually a bit more entertaining than normal tic-tac-toe, but it's also much harder.