What is a creative way to give out prizes at an employee party?

We usually give out gift cards as prizes at our summer employee party. We want to make sure that everyone gets a prize, but want to do something more creative and entertaining than drawing names or a raffle. We have extra prizes for people who participate in other activities. The party will be held at a baseball game in our own exclusive area with tables and a buffet. We are expecting about 75 employees, ages ranging from 17 to 55. Thanks!