Dragon Egg

The Dragon Egg is an item first mentioned by Notch on the 27th of October, 2011 on which Notch was supposedly working before the feature freeze, though it seems to have been worked on during it.

This block first appears in Beta 1.9 Pre-release 6, and appears on top of the Bedrock portal back to the Overworld created in The End after the defeat of the Enderdragon. Left or Right-clicking it seems to cause it to teleport to a place nearby but it can be picked up with a the aid of a Bucket. As of Pre-release 6, the Dragon Egg has no use.

Trivia

 * In Beta 1.9 Pre-release 5, Enderdragons dropped a single block of Obsidian. Considering that The End had an abundance of Obsidian and therefore a single block of it would be useless to the player, this drop was speculated to be a placeholder for another item. Though the Dragon Egg should fill this void, Enderdragons do not seem to drop anything upon death (other than experience) as of Pre-release 6, and instead the egg is a block created seperately from it.
 * It can teleport up to five blocks either direction along the y axis, and up to 15 blocks on both the x and z axes. This gives it a 31x31x11 volume of space where it can teleport to.
 * The egg may teleport into open air, causing it to fall to the ground, but not crack.
 * Redstone currents cannot pass through an egg block.
 * Attempting to push it with a piston causes it to revert into item form.
 * Destroying its accompanying Overworld Portal with water or lava will also cause it to turn into an item.
 * When hit whilst in survival and holding no tool, the egg will appear to teleport a short distance, similar to an Enderman. When hit with a pick, the egg will be destroyed.
 * It can be picked up in a similar way to sand or gravel, by letting it fall onto a torch. This works with all non-solid blocks.
 * It remains to be seen if the egg will have a purpose of its own or if it will serve as some kind of ingredient.
 * The writer of the Minecraft comic WonderCraft, Samcube, was submitted by Mojang to create official Minecraft posters for possible purchase. In part of these works, one can see an area with an Enderdragon and a chicken. In the same scene is a purple, egg shaped block like entity near the chicken. It is possible that this could be the Dragon Egg.