In a circuit I was making, I was using several sticky pistons pushing&pulling others, in an ascending tower... Then, I downloaded and ran snapshot 13w09c and I found a bug that didn't show off in snapshot 13w09b. A sticky piston pulling another sticky piston makes the 2nd one (the sticky piston being pulled) vanish.
Duplicate of MC-9460, please use the search function to see if your bug has already been submitted. Currently over 53% of tickets are being closed as duplicate.