I needed an extension cord for something, so I went to the garage where I had use plugged in for a kind of a single-use purpose.
I was going to use it inside, so I needed to clean it off. Here is what I found:
One strand of the wire didn't get wound in, so in the insulation coating process it poked through. It's been in use like that for a long time.
I don't recall getting shocked from it...
Note that the strand is on the HOT line!