Not everybody can afford a prosthetic arm. Most people can't. It's a good thing Lego are so versatile. Now you can build your own!
Max Sheperd is the guy responsible for this awesome Lego robot arm. He says it's built to be a 1:1 scale, has 12 degrees of free motion and tons of articulating joints and fingers.
As you can see in the video, the fingers have enough strength to hold a water bottle, little rubber tire wheel and tape without any trouble. It does need a little bit of assistance from a human helper, though. But don't go expecting the robo arm to carry your bags for you yet, Shepherd says it can't carry more than a couple of pounds.
The main purpose of this project was to accurately mimic the full range of motion of a normal human arm and hand. The secondary goal was to maximize speed and power, yet maintain a consistent ratio between the two for demonstration purposes. It is important to note that it was designed as an above elbow prosthesis, and the yellow shoulder is only meant to act as a static model.
The arm isn't really that fast, but honestly, what do you except? It's made out of Lego and it's controlled by a "rudimentary cluster of switches and joysticks with a 4-motor air compressor with pressure-regulation."
Give me two of these and make the arms faster, stronger and powerful enough to punch through a wall, and then I'll cut my arms off.