Slimeball

The Slimeball is an item dropped by Slimes. There are no uses for it so far. Notch confirmed that they are going to be craftable in a later beta update. Some players use Slimeballs in mods.

0-2 slime balls will be dropped when a small slime is killed. Only small slimes will drop Slimeballs on death, and larger slimes will duplicate into smaller slimes (Beta 1.3 update changed it so no matter what item you use to kill a slime, the slime will still split). As slimeballs come from Slimes, they are a renewable resource.

Some users use these as tokens or cash in multiplayer servers, since it has no use and is more realistic, since server mods do not use up inventory space. When in Single Player, some players use them to show how many slimes they have killed.

You could also use it on ice, to bowl. As it looks like a green bowling ball.