Attempting to pull a cauldron with a piston that has a water source block above it, causes an instant game crash and can permanently currupt the world. 

Build the same device I did in the first video to do this. *Do not attempt this on a world you care for!*

The first video is what has happened to one of my worlds after I discovered this bug. (Sadly it’s my main redstone world.) The second video is of me executing the bug.