Do a Google search on Bruce Evans, knifemaker.
Bruce used to make a few knives from crescent wrenches. always telling folks they were just junk and not real knives. Think he charged $50 for them.
I make a few knives from RR spikes as trade goods with some of the shops that allow me to pick through their scrap.
Bill Cottrell made some spike knives adding a piece of good steel in the split spike- pretty darn good knives.
There was a local challenge to build the best spike knife- won by Dave L. He made a spike from Damascus and then used that for his effort!
I have an 18 inch busted Crescent wrench in the shop by the air hammer- may make a junk knife, or not, or a tomahawk, but I see it sitting there quite often, Usually makes me smile.
Experiment.
Play.
Have a good time.
ENJOY!