Jeshii, a teacher in Japan, discovered his students playing "battle pencils" ("Batoen") a game where you "roll" a standard-shaped hexagonal pencil and then gain or lose points based on the face that comes up. They're like long dice.
The rules are pretty simple. Your character starts out with 100 hit points (this is written on the pencil, so some characters might have more or less). You can play with 2-4 players. Start off by doing rock-paper-scissors. Winner rolls his pencil first. Then you do what it says on the side that faces up. Usually this is 'miss' or 'everyone takes 50 damage.' But it can also target certain types. Each pencil has a star or a circle band. So sometimes it will say, 'all circle banded characters take 40 damage.' Sometimes, the monster has special abilities. Like, 'roll one more time, and use the effects below' where there will be a different set of abilities. As you can guess, if you lose all your hit points, you are out. Generally, after you roll, it is the other guy's turn. When you gain hit points, you are capped off at 100.
Also, there is equipment, magical items, pets (all caps you attach to an end), and even helping erasers!
Update: Neil sez, "Pencil Cricket (cricket played with one or two six-sided pencils as "dice") has been around for ages, very popular with schoolboys in the UK at least, back when there weren't none of these fancy PSPs and internets.
"My dad remembers playing it aaaaaaages ago, complete with the fine detail of individual 'player's' careers, stats sheets and seasonal tournaments."