NOTE: THIS GLITCH HAS BEEN PATCHED!
Block Data Value ChangerDescription
Due to a neat glitch it is discovered to be possible to change the block data value in Minecraft. This affects wool, stone bricks, logs, slabs, and many other blocks. It can be used for useful things like changing the color of a block of wool or changing whether a stone brick is mossy or not.
It requires sticky pistons, a bit of redstone dust, a few redstone torches, and water.
If it doesn't work try moving it to different coordinate areas.
"Note that it's sensitive to orientation (don't rotate it) and to chunk borders (move it a bit if it doesn't work)."-Zhul
Try not to build it in the +X & +Z direction.
Reference for all the different block types able to be made. (From Regular Hexahedron)