This was maybe 15 years ago:
I was walking back to the train through Union Square Park carrying a big black baseball bat I had just purchased. (This was before the re-emergence of kickball and I don't like the stingers you get from aluminum bats.)
Like others have described, I saw someone ahead that looked familiar. But I just couldn't place her. Then, just as we were about to pass by each other it clicked. "Oh yeah", I thought to myself, it's Chynna Phillips from Wilson Phillips.
Having filed it into the "who cares" section of my brain, I closed the encounter with a terse nod of recognition and a slight wave of my hand. It was reflexive; how you react when you pass an acquaintance in the hall. Unfortunately (for everyone) the hand I raised to wave was also carrying the bat.
She started screaming and covering her head with her hands. At first I was stunned by the reaction and could not figure out what was going on. Then it all made sense. My apologies and assurances only made it worse, so I simply turned away and walked down to the train.
An honest mistake about which I felt awful for a good long time.