Hi Sue,
I'm not sure if this is totally unique but there is a chat game called blackjack where as a CM you ask everyone to give you 2 numbers that add up to 21 or subtract to make 21. For example 53 and 32 (subtracted makes 21!) or 7 and 14 (added makes 21). When the two numbers are called in the chat box the winner writes BLACKJACK and the bonus is paid.
Hope this helps!