Slime

The Slime is the fifth hostile mob, and was added on July 23, 2010 (Seecret Friday 6! Alpha 1.0.11). They appear as green semi-transparent cubes. Slimes come in four official sizes: huge, big, normal, and small. Small Slimes do not make any noise when jumping, while larger Slimes make a wet slapping noise. They are the first hostile mob that can spawn in both light and dark areas. These creatures are only naturally found deep underground in the bottom 16 layers of the map. They usually spawn in large, cavernous spaces or in open mines. This is partially caused by the fact that a large space is needed for them to spawn.

Attacking a slime will cause it to break into four smaller sized slimes. after the beta 1.3_01 update killing a slime with anything that deals more than 1/2 a heart will not yeild more slimes or slime balls.Snowballs and eggs can kill slimes, see weapons for damage values with different weapons. Currently, Slimes do not grow larger over time. The small slimes are harmless and can only push the player around. The smallest variation of slime are often kept as pets by players. This is because they do not do any damage and follow the player around harmlessly.

Slimes of any size will begin to take burn damage upon touching lava and die moments later without splitting into smaller slimes. Slimes cannot swim; therefore, they will drown if they are completely submerged in water and will be unable to jump out. Slimes have the ability to climb ladders, enabling them to follow the player out of caverns.

Killing a small slime yields 0-2 units of Slimeballs, which currently serve no purpose whatsoever.

The slimes spawn and attack aggressivly in peaceful mode(uncomfirmed if it's intended, most likely a bug)

Drops
Beta:
 * 0-2 units of Slimeballs (Small slimes only)

History
When slimes were first introduced, they spawned at a very high rate. This caused Notch to limit slime spawning. However, it appears that he incorrectly calculated slime spawning, leading slimes to spawn only in strange locations. This eventually caused Notch to completely disable natural slime spawning. Later, Notch confirmed in Coesquest's livestream that slimes have been returned as of Beta 1.2_01, but are very rare. As of Beta 1.3, Slimes spawn have been increased once again, appearing much more commonly than in 1.2_01.

Trivia

 * Even as of Beta 1.3, Slimes are able to spawn on peaceful, and even on Peaceful, Slimes will attack players without any provocation.
 * By editing the mob's files, it is possible to make slimes much larger, some values creating 50-block-high slimes.
 * As of Beta 1.3, slimes in multiplayer that split will only be visible to the player that caused them to split. Because of this, they will not take any damage. Because they are located on the client's side, the player can only remove the slimes by exiting and re-entering the server.
 * Slimeballs can be farmed by punching Slimes to death instead of using a tool like a sword or an axe. This guarantees they will split into four more slimes, instead of merely dying. This means: 1 Huge Slime = 4 Big slimes = 16 normal slimes = 64 small slimes = 0-128 drops.
 * Slimes may have been inspired by a number of classic gaming monsters: Their shape and size resemble that of Gelatinous Cubes from Dungeons & Dragons, and their splitting behavior resembles that of Zols from The Legend of Zelda and Puddings from Nethack. The name and the large, cartoonish face may be an homage to Yuji Horii's iconic Slimes from the Dragon Quest series.