This happened a few weeks ago, during the early morning hours. I was heading toward the back of the store to put up some signage, a few minutes passed by, and the cashier called for backup. I proceeded to the front of the store, and an old man came to my register.
I asked if he has a customer card, to which he responded, "No, and I don't want one. I've spent 10 minutes in this goddamned line and now I just want to get the hell out of your goddamned store." In respond, "Ok sir," treating him as if he is a normal person. (It should be noted that only 2 minutes passed by, not 10, as there was no line when I left the customer service desk a couple of minutes prior. I knew there was no way I could reason with the customer so I let him "win"). The man purchased one item; it totaled to $11.40 with tax. He handed me a $50 bill and 40 cents. I counted his change ($39) in tens, fives, and four ones and stacked the money neatly before him. He said, "Great, now I have to recount the change since you can't count it right." I watched as he counted the change, smiling the whole time. "Did I count it correctly sir?" I asked politely. He responded sharply, "Yeah I guess you did," yanked the receipt out of my hand, and yells, "Let me tell you, you're one of the most sarcastic sons of bitches I've ever met!"
I reply, "What exactly did I do wrong sir?" He replies, "You know exactly what you did wrong you little bastard. I spent fifteen goddamned minutes in the line while you took your time, you can't count the damn change correctly (this after admitting I did count it correctly),... followed by a stream of profane insults, which I fail to recollect. Then he asked to see a manager. When I told him I am the manager on duty, he barged out of the store. I chuckled.
In other news, the next morning a customer told the GM to "go fuck herself" because she would not return a half-empty toner with no receipt and no way of proving it was purchased for $150 as the customer claimed. (It rang up for $15). Clearly a dumpster-dive.