I had a habit that when I would ring up a single pack of cigarettes I would kind of gently drop them on the counter for the customer. nNothing major, y'know, just saying, "Hey, there. They are for you."
So, I did that with one lady, and OMG SHE FREAKS ON ME! "How DARE you throw those at me! That is ASSAULT! I want Security in here!" on and on and ON until one of my favorite officers came in.
He looked at me, looked at my line, looked at her and said "Lady, if she threw them at you, she probably had a good reason to," and left it at that.