With a round and a flat file you can turn a rake tine into a pick in 15 minutes.
If you can find street-sweeper tines, you can bend them to make good turning wrenches.
It is not an efficient use of time compared to buying, but still fun.
Someone you know has wipers that should have been been replaced years ago; do something nice for them, and get enough pick-stock to last for years.
Bike spokes are also useful, but a bit more work to flatten/grind and shape. (Great for tension wrenches, though.)