Minecraft traps

Materials: redstone wire,
redstone torch,
pistons,
1 sticky piston,
sand,
and blocks.

First, make a hall way. On the ceiling of the entrance and exit, or the on top of the switch (not recommended) place a piston or two. Now, in the middle put a pressure plate and wire it to a sticky piston. The sticky piston should have a block at the end. After that's over, wire the other pistons to a redstone torch. The wire connecting to the torch should be up a block so, when the sticky piston extends it should cancel out the circuit. The other pistons will then retract. On top of the piston opening part, put sand so when the pistons open, sand will fall on the person, or seal off the entrance or exit.

Bird's eye view of the trap. I did a double piston at the end of my hall. The sand also fell.

Side view of the trap's wiring so you can so the different heights every thing is at.
This is the view of the hallway.