Soul Sand

Slow sand (aka "mud", "hell mud" or "soul sand") is a brown-grey dirt-type block, found in The Nether.

Properties

This material has several unique features:
 * It slows the movement of any player or mob.
 * Players sink slightly into the block while walking on it.
 * Unlike most ground blocks, it is not weak to shovels. Even with a Diamond Shovel it takes several seconds to destroy a block.
 * Sneaking on a slow sand block will not prevent you from falling from the block. (Bug?)
 * It reduces fall damage.

Uses

There are currently no recipes involving slow sand. It is an effective building material when creating a dock, because boats are not destroyed when colliding with a slow sand block at high speeds. It can also be used to prevent taking damage from long falls. Also, slow sand will slow things down more when water is flowing atop of it. This could be useful for making drowning traps more effective against pigs. The slowing effect can also be used to fight large amounts of mobs at once, especially using your bow.

Trivia

 * The texture resembles a collage of faces. These faces are said to look like those of Creepers.
 * This block stopped generating in the v1.2.0_01 update; in its place, gravel was generated. This was fixed in the v1.2.0_02 update.
 * The first appearance of this block was on Notch's blog.