What are some good games to play at picnics?

My family's having a reunion and we need some good games to play. Nothing stupid... we have a plethora of stuff for the little kids to do, like pi�ata's and stuff. And we have beer pong and other things for everyone 18+. But we're really crazy and we need some FUN stuff to do. It;s gotta be something random, like mattress racing down a hill or something of the sort... fun, yet crazy and not something your mother would advise you to do.