While most people think of Magic as something serious (or at least serious-leaning), there have been more than a few silly sets released just for kicks.
There are a ton of Unglued cards that are worth mentioning for their outlandish designs and artwork. The 99/99 Big Furry Monster comes to mind, which required you to play two halves of a giant card and cost 15 black mana.
Chaos Confetti is the one that always sticks with me, though, as it's the only card that you have to actively destroy in the real world to play! I have to wonder how many people have actually followed the directions on the card during an Unglued game?