Most doors put function over form, but the Ping Pong Door by Tobias Franzel serves a dual purpose. It boasts an inner panel that flips down to create a functional ping pong table. Just prop the plastic net up, get your paddles, and you’ll be ready to play. However, we do recommend installing this in adjacent rooms that have enough space to move around, rather than a narrow hallway. Continue reading for more cool multi-purpose gadgets.