Farkle is a Fun (and Very Cheap) Dice Game

All you need to play Farkle are 6 dice and a piece of paper and pencil to keep score. You just can't get much cheaper than that. You can see the rules and everything else you want to know about the game on Wikipedia.

If you play with kids, you can use it to help with mental addition and probability. Or, you can just play it for fun!