The Clown Prince of Crime
Super Freak
Didn't Anakin find C-3PO pretty much complete, circuit wise? I think it was only the plating and reprogramming that he did, so technically he didn't build him completely from scratch.
C3PO existed before Anakin, he was protocol droid, but Anakin collected the scrap parts and rebilled C-3PO. Protocol droids were normally designed for light duty in comfortable settings, so Skywalker modified C-3PO so he could withstand Tatooine's harsh environment. He also modified and improved his cybernetic hand years later, which was the only mechanical prosthesis that wasn't outdated like the suit he was given by the medical droids after he was almost killed by Obie Wan. Same technology that was used on Grievous.
I'm not sure that's as impressive as Rey being able to fix the Falcon, given Han and Chewie didn't know how to fix the issue, and they knew that ship better than anyone, with the exception of Lando...maybe. Being able to fly such a large ship the way she did, and beating the expert First Oder pilots that were flying smaller ships was probably more impressive than fixing the Falcon actually.