shave the cream off the balloon without popping it
Blow the balloon up and cover in shaving cream, then give the balloon to the contestant along with a razor. Have the contestant/contestants completely remove the shaving cream using only the razor without popping the balloon. First one to remove all the cream without popping the balloon wins! If one of the contestants pops the balloon before successfully removing all the cream they are immediately disqualified.
Take the razors before hand and break the razor blades so that there are sharp points in the blades. This will make it more difficult to shave the balloons.