1. The "gimme" one.
There are a few different ways this person tries something. Sometimes they start of telling some kind of sob story in order to get some sympathy and break down the walls you were taught to leave up for customers. Maybe their dog died, or their newborn baby has been keeping them up all day and night. Either way, they learn very quickly that that tactic isn't going to work. So they move on to anger. And yelling. And fist waving. And finger pointing. This is the most frustrating part because all you're allowed to do is smile and be polite. And then, of course, they want to speak to your manager who tells them the exact same thing you did. (They don't end up getting free stuff).
2. The overly comfortable one.
Whether it be something good or bad, there's always at least one customer a day who says something so unusual, you don't know what to say back. When you ask questions or start a conversation in order to try to understand, you only end up more confused than you were. So you just awkward laugh and shrug it off, asking them if they want their receipt. Best case scenario: they leave; worst case: they stand there and stare at you.
3. The creepy one.
Even if you don't work in customer service, you know EXACTLY who this is. Race, gender, and sexuality don't even matter. This customer always says or does something that is SO uncomfortable it makes your skin crawl. But you can't even get away from them because, well, it's your job. So you just take it in the instant, but as soon as they walk out the door, you tell all your coworkers what just happened and try to move on as best you can.
4. The early bird.
This person comes in BEFORE you're even open for service. He or she then gets mad that they can't be served at that very second, even though the OPEN sign is clearly not on, and the hours of service are clearly written on the door. So then you end up serving them anyways, but when told they have to wait a few minutes for the order to be completed, they get angry. Sorry, sir, you came into my store ten minutes before we opened, and don't want to wait three minutes for a pizza.
5. The right on time bird.
If we close at ten, you bet there's going to be someone coming in at 9:55 p.m. when we're getting ready to shut everything down and start closing. And of course this one orders something complicated that makes you reopen everything and it take 15 minutes, and by the time it's all said and done, he's mad he had to wait. But you serve him anyways because TECHNICALLY, yes, you're still open. And you have to do it with a smile.
This being said, people who work in customer service have to deal with a lot of anger, sass, and crazy. Please try and make their job a little bit easier for them.