I work at a pretty small theater, and today a customer wanted to buy a $120 worth of gift certificates.
She wanted to pay with a check, and I looked at my manager, who confirmed, "I'm sorry, we don't take checks." The customer looks at her, and back to me.
"I don't like her." she says, too serious to be joking. And that's it, nothing else. Just a small unpleasantry that made the day worse.