I have always worked in some form of customer service, which has all kinds of...fun moments. Highschool through university I worked in restaurants. Got the full gamut of rude customers, customers rolling in thirty seconds before close, etc. Had a customer try to pay us in cocaine once, which we do not accept as legal tender.
I am in [luxury] hospitality now and have had to deal with all kinds of entitled jerks and celebrities. Including some heads of states that I have very strong negative opinions about. The mid tier CEOs are the worst though, because they think they are far more important than they actually are. Had a guy call the police while he was checking out because he didn't want "a foreigner" handling his luggage.
Saved us the effort of blacklisting him, because the police obviously escorted him out instead.