I don't normally feature many strange games that require you to buy expensive equipment to play them...but I feel that Spikeball is so good it has to be featured here. Spikeball is a beach game that is kind of like beach volleyball only there isn't a net, at least not one that is strung between two poles that you have to hit a ball over. In Spikeball the net is replaced by a round, ankle high trampette. The teams, consisting of two players each, fire the ball into the trampette with the aim of making it impossible for the other team to return. Like volleyball each team has two touches of the ball before the third one that must direct the ball against the trampette. Unlike volleyball team members can occupy any space in the game...there is no court.
You can get official kit from Spikeball.com but if its not available in your area you could always improvise with a tennis ball and one of those small, round exercise trampolines.