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.

[youtube=http://youtu.be/zKakpY2oZqI]

Wei Xinlong, a senior at Northeast Normal University in Changchun, built this for his girlfriend Sun Shasha. Methinks that if this is real and works well, the world is soon to see a whole new wave of tablet PCs.