Player can use this bug to go down a "ladder" made of gravel or sand blocks.
How to reproduce:
- Stand on a pile of gravel or sand blocks.
- Sneak on the ledge
- Remove a block underneath you. Not the one you are standing on.
- The block you are standing on will, naturally, fall 1 block high, but you fall 2 or 3 blocks.
- Repeat the process until you get safely the ground.
Video showing the bug: http://youtu.be/_fgOQ5kM14M (1'20")