I can still be surprised at how customers choose to interact with clerks.
There is the scenario where a clerk says "hello" in a friendly manner without sales pressure and the customer grunts back "I'M JUST LOOKING I'M NOT GOING TO BUY ANYTHING." My co-worker responded to such a comment the other day by saying "I was just saying 'hi'." Her tone was calm and civil. The customer said something like "oh, hello."
I was having a conversation with a customer about smoothies. We were talking about how much we love them because we consume more fruits and vegetables and avoid breakfast traps like donuts and sugared pastries. We feel awesome and healthy. The customer mentioned how it was weird at first because she missed chewing. I responded by telling her that I sort of "chew" my smoothies. Another customer, passing by with a shitty scowl on her face, said something sort of under her breath but still directed at us. Something like, "Smoothies aren't food!" And she kept going. What a shithole. Here we are, making better lifestyle choices, feeling a little good about it and Poopypants has to butt in just enough to crap on us. She sucks.