Some forms of comedy are just timeless.
Pie Face from Rocket Games is like a (mostly) harmless version of Russian roulette for kids. Players take turns placing their faces in range of a mechanical hand holding whipped cream in its palm. The hand is controlled by a spring-loaded trigger that releases after a randomly determined number of turns.
This little boy and his grandfather took a shot at the game, with predictable results. Watch the man literally ROFL after hitting his grandson in the face with whipped cream.
The cream isn't included with the game, so if whipped cream is too predictable for you, the possibilities for punishment are endless -- fresh mud, snow cones, fake dog poop, you name it.