Water gun fights are a great way to beat the heat and demonstrate your military skills. But the pump-action water guns we grew up just don't seem as impressive anymore. What if you could turn a plastic toy gun into a motion-activated water gun turret?
According to Jason Poel Smith for Make Magazine: "The gun is controlled with an infrared motion sensor and an Arduino microcontroller. The motion sensor detects when someone walks in front of the gun, and then the Arduino activates a relay that is connected to the trigger and fires the gun. You can set it up in a hall or in a doorway and it will shoot anyone who walks by. This is a fun way to prank your friends."