You could have a door prize (in a bag, so they don't know what it is) and if it is a theme show have them pass the bag to the left every time you said a certain word. ("every time I say "chocolate" pass the bag to the person on your right")
I say a game the other day that the consultant called "poker". She took a deck of cards and if the customer asked about a product, she gave them 1 card. If the customer asked about the business opportunity, she gave them 2 cards. At the end of 5 or 10 minutes the customer with the best poker hand won the prize. I was attending an Arbonne party, but this could be adapted to any type of party. You could even give cards to anyone who books a show.
When I am demonstrating stoneware, I will tell about the stones, (food cooks more evenly, they are guaranteed for 3 years, etc) making sure I tell them 10 things from the "reasons to own a stone" information. Then after the demo, I ask them to list the top 10 reasons for owning a stone. The customer with the most correct answers win the prize.
I would love to have any other party suggestions anyone has.