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.
From the submitter:
A while back I decided to see how my coffee maker worked. I busted it open and by the time I figured things out, I couldn't put it back together (broken). So I decided I didn't want to buy a new coffee maker and I built this stand for the machine innards. The reservoir was built into the old machine, so I had to add the bottle to hold the water as it heats up. It works great!