Marbles <3. I got 20 tickets for guessing correctly \o/. Guessing 0 or 1 seems like a good strategy. Would be cool if you started out with say 5 tickets and playing a game costs a few tickets.
One of the original ideas was that players would get to buy stuffed animals with the tickets, but we clearly scrapped that idea. We thought that keeping the tickets in would be a nice way of giving something extra than "yay, you guessed correctly" :P