3D printers are great for making things, including more of themselves. The first really accessible 3D printer, the RepRap was designed to be buildable from locally sourceable components - metal rods, bolds, screws, and wires, and the rest can be run off on another 3D printer. There is even a variant called the JunkStrap which, as the name implies, involves repurposing electromechanical junk for basic components. There are other useful shop tools which don't necessarily have open source equivalents, though, like laser cutters for precisely cutting, carving, and etching solid materials. Lasers are finicky beasts - they require lots of power, they …