Thin Tool Steel
Many years ago, when I was still young and unpardonably stupid, I was fresh back from overseas with the USAF, camping at the Grand Canyon with my family, and had with me a pair of excellent Gerber hunting knives, a Shorty and a Mini Magnum, that I'd picked up on base while at Ramstein AFB.
I had been practicing with cardboard targets. The Mini Magnum was a little smaller than the Shorty, and though the balance was abysmal for throwing, I had found a way to use that imbalance to calibrate a fairly reliable throw. I was getting four out of five to stick.
This gave me just enough confidence to show off my new-found "skill" (and my entrenched foolishness) by throwing the knife at a pine tree.
It stuck the first time. Impressive penetration. A perfect throw. Snapped off the first inch of the blade.
I remember the feeling as my stomach fell through my feet.
I worked the end of that knife, gently, with a file for days, gradually re-profiling the tip until it looked like it had been made that way. Got a very serviceable edge on it. It looked like a totally normal kitchen utility knife with an extra heavy handle. I couldn't bear to carry it after that. Gave it to my mom for the kitchen. She loved it.
It taught me something about the characteristics of thin tool steel (as the Gerbers used back then).
It also cured me of throwing knives.