Play Petals Around the Rose.

You can only be told three things: the name of the game, the fact that the answer is always even or zero, and the answer for any particular throw. If you figure it out, don't tell anyone else how, let them get it themselves. The theory is that the smarter you are, the longer it will take you to figure it out.

Play it here: http://www.borrett.wattle.id.au/computing/petals-j.htm
Read about how long it took Bill Gates to figure it out here: http://www.borrett.wattle.id.au/computing/petals-bg.htm