When you place this:
>T
XL
Where:
> = Piston facing Right
T = TNT
X = Any Block
L = Lever
(Side View)
and Trigger the Lever, the TNT gets primed AND gets pushed by the Piston, Creating a duplicate. However, if you want to destroy/collect the TNT block, it disappears with no drops.
Related issues
Comments

Duplicate of MC-151 , please use the search function to see if your bug has already been submitted. Currently over 35% of tickets are being closed as duplicate.