Piston with no head, put a block in front of it then re activate the piston, and it breaks the block even if it is bedrock.

How to do it: 1.Make a server with world edit plugin, or put modloader in your client then add world edit in your bin folder.
2. Place a piston, and place a redstone torch under it, or make it activated/extended somehow, then put a sand/gravel/anvil block on top of it.
3. World edit using: Select the whole thing that you built, and type //set 0
then //undo.
4. The anvil/gravel/sand is gonna fall down, and the piston is gonna have no head. break the anvil/gravel/sand block.
5. Place any type of block in front of the headless piston, then re activate it. It will remove that block what ever it is.
Solution : World Edit plugin maker fix that bug
I don't know what mojang can do with it because minecraft has been not programmed to handle vanishing blocks through commands.