Make a 1x1 tower with a ladder up 30 blocks. Keep a 2x2 hole and made 8x2 block spurs off of the platform. Make 2-blocks high walls around the spurs. Fill in the area between the walls to make it a square. Add a bed to sleep in to set spawn if you are killed or in case you fall off. Add walls 2-blocks high walls around the raised platform. Add roof and water at the end of the 8x2 spur,s than remove the bed and the tower. *Don't not add walls to the drop area. No enderman are produced. Collecting loot may result in death. Not the best design for a drop trap. Then your ready to be a dick !
TNT Trap Hole
Dig a hole at least three blocks deep place your TNT in the middle, then sand or gravel on that, then a pressure plate on top. Viola! Now just wait for someone to fall in. This is best used in narrow one block wide passages, or even better in front or behind a door.
Drop Hole Trap
Dig a hole down to bedrock and cover the top with something like ore or other things of value. Stay at the bottom intil someone breaks the first rule of minecraft to collect loot. You could also add lava if you don't want to live there.