Don't say the word "yes" or else you'll lose your opportunity to win a prize!
Yarn A prize for the winner
Take a piece of yarn and tie it in to a necklace. Give each person at your party a necklace as they arrive. Instruct players that they cannot say "yes", "yeah", "yup", "uh-huh", "si" or anything that means yes. The only thing they can do it shake their head to mean "yes". Everything else is considered saying it. If a player hears another player say "yes" or one of it's derivatives, they can take their necklace(s) from them (if a player has several they have to give them all up) and they become yours. The person with the most strings by the end of the party gets the prize.
Make the necklaces out of green yarn.
Yarn Nicki, Tennessee