Protect your room with a centipede dropper! Anyone who enters will have a centipede dropped on them!
It's a very simple machine, but can give a good scare. A cup holds the centipede, a servo motor flips the cup to drop the centipede, and a distance sensor senses if the door is opened. If the distance is less than a certain amount, the arduino turns the cup 180 degrees. After a second, it returns to its previous position, with the cup facing upwards. The machine will be dormant for five seconds, making sure the cup doesn't keep dropping centipedes. I glued the distance sensor to the bottom of the cup so it takes minimal space.
To use it, just flip the switch to turn the device on. Place the toy centipede in the cup. Then, wait for invaders.