TNT cannons have been "fixed" out of the game. The most complicated things I made we automatic street light (before light detectors were given an inverted state) and a piston-harvest farm.
WHAT. What heresy is this? D:
Also, I went venturing into the nether to get some nether bricks. I brought my newly-made enchantment with me. You can guess how that went. But hey, I did get the "return to sender" achievement in the process of blindly falling off a cliff into magma.