Instructables user cbaabc73 came up with a cheap and easy way to turn off outlets when you aren't using them. He built it after noticing his wife kept leaving the curling iron plugged, which can be extremely dangerous. This DIY project takes only basic tools without the use of soldering.
Deviant Artist Midnight Angel put together an arm blade stylized after the ones used in the Assassin's Creed video game series. Using a drawer opening mechanism, a spring for a screen door, and a throwing knife, the weapon works surprisingly smoothly. The full instructions are on Angel's page, and you can see it in action below.