Concrete nails
Concrete nails, hex wrenches, drill rod, HSS metal machining bits, and other materials can be made into different kinds of turning tools.
My preference is for HSS bits. 1/4" x 2-1/2" bits are about a dollar, and the quality is incredible. They come in round and square shapes. They don't have to be tempered, just grind and use. They don't easily lose the temper when grinding. Don't dip in water as you grind either, if they are hot enough you will have microscopic cracks in the edge.
You will need to make a handle for the HSS bits, just like any of the other materials.