Put Loctite on the nut that holds the speedo cable to the back of the speedometer. I don't know what I was thinking when I did that. Luckily, it didn't bond well and came right off the next time I took it apart.
Had the camshafts out for valve adjustment and reinstalled one of them 180 degrees off. Something was bothering me about it, I checked and re-checked it, realized what I had done and fixed it before anything bad happened.
I once locked both sets of keys inside the car. On a ferry on Delaware Bay, a hundred-plus miles from home. That had a good ending too: a security guard with a slim jim had it open in no time, said it happens all the time.