I used to work at a college bookstore. This happened right at the end of my shift, which coincided with closing.
It was a very busy day, since school has just started. A lady comes to my register with a number of items, then decides she wants to go look at some clearance items.
I agree to let her leave her items at the register, since there isn't a line, and there aren't any other customers.
I assumed she would only be a couple minutes. Nope. She took a good 10-15 minutes to look at stuff.
Then, to make it worse, she decided it was socially acceptable to pay in one dollar bills. Her total was 62 dollars.
It made for a good laugh, but it was annoying nonetheless.