A guy in his bedroom, with a dangerous sleeve weapon. No, you're not watching Taxi Driver, but rather, YouTube user Angelegend showing off his arm-blade. You know, like the ones in Assassin's Creed.
The arm blade was created from things like a door hinge, which doesn't sound easy. According to Angelegend, "It's a bit complex, but if you're not afraid to get messy and make some mistakes then check the link... for detailed build instructions. Be safe and have fun."
Not really afraid to get messy and make mistakes. I am, however, afraid of a blade impaling itself into my palm.
This isn't the first of these Kotaku has posted, and there appears to be a whole Assassin's Creed arm blade subculture.
Assassin's Creed Arm-Blade with build instructions [YouTube -- Thanks Jake!]