A few days ago I bumped into the story of a Chinese farmer building his own prosthetic arms. I am completely in awe of this man. He is a real life version of Tony Stark in a cave with a box of scraps.
Sun Jifa is completely self taught. Frustrated by the largely cosmetic arms he initially got after he lost his arms from an explosion, he tinkered with them until he created fully functional arms. If fact his prosthetic arms are so good others have been seeking him out for their own pair. He has created a successful business and is now able to support his family.
Below is a video of his story.