This works best outdoors.
Start by giving everyone a balloon and a length of string about a yard long. Blow up the balloon and tie one end of the string to the balloon and tie the other end around your ankle. The balloon should not be close to your ankle, leave about 12 inches or so of string between your foot and the balloon.
Have everyone stand in a large open space. The object is to stomp on everyone else's balloons and pop them.
The last one with an un-popped balloon wins!
Click this animated image!