1. Changed oil in 72 Challenger and didn't check to make sure the oil filter rubber seal came off oil pump with filter. Put the new filter right on top of the old seal. 100 miles later it all came off in the middle of the road.
2. Showing off in my 1967 Polara 383 when in my teens. Put it in neutral and revved her up hoping to get a scratch by dropping it into drive. Drive shaft dropped like a rock right onto pavement.
I did something similar at age 15 with my 57 Desoto. --I was showing off by getting one tire spinning in drive at wot. After a 95 ft long black mark was made I hit the reverse button and the trans went into neutral instead. Nothing broke but I never tried that again.
With my new 69 super bee-- I many times ran the engine to valve float and power shifted. Had the clutch and trans sincros replaced (under warranty) twice in 11k miles. That 383 would not break under my teenage foot.