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.
Instructables user hanlin_y did the math and realized that alkaline batteries are one of the most expensive forms of power that consumers can use. So he/she/it came up with a solution to power your parts even if they don't come with an AC adapter. With a wall plug, wires, and bamboo strips you can run your electronics off the grid; saving money and the environment at the same time.
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.