Quiver

The quiver is a sprite located in Minecraft's items.png resource file. It has no actual item in-game and thus is impossible to obtain. Jeb has confirmed that he is not planning to add quivers.

The quiver sprite has been in items.png since the Indev phase, along with another unused item, the leather-chain armor.

Trivia

 * In Legend of the Chambered (an abandoned RPG that Notch made), there was a quiver item available to be picked up as loot. Notch reused the sprite from that game and put it in Minecraft, albeit flipped horizontally.
 * The Quiver is actually obtainable in Minecraft Pocket Edition through inventory editors. However, if you sit it in your hot bar, the game will freeze. The quiver is not actually intended to exist in game, it is just a blank file using the quiver sprite.