Here's a sort of semi-rant/story from today.
So I had this elderly lady come in, order her drink and then say "my husband is going to get a gift card" I said okay, and I swiped her starbucks card (I hadn't yet pressed the button for it to process payment from the card) My pos then decided to have an error and restart itself spontaneously.
I said sorry we're going to have to move over to this till because this one is having an error. Her husband moves over to that one and she steps back to one of the waiting spots, so I punch her drink in (since it didn't go through on the other pos) and he says he wants to load 30 onto the gift card, so I ring that in. It prompts me to ask for a name, and he gets huffy asking why I need his name and I say that it's for when they have the drink ready, he shows me his name on his card and goes to pay with his visa. The total was like 36$ and change, and he says "why's the total 36?!"
I said 30$ for the card, and then your wife's drink. He starts raising his voice, not yelling, but getting there about how he just wants to buy a gift card, and he turns to his wife and goes "did you get a drink?!" She says something and he turns back to me and says she paid for her own drink.
That's when I realize they wanted to pay separately, so I ask her to come back up because her order hadn't gone through. So she pays for hers, then I ring up his giftcard. The whole time he's being huffy, and then as soon as he's paid, he's suddenly cheery and says have a good day.

It was so weird. He's snapping at me a kinda freaking out and then all of a sudden nice at the end, and I'm just thinking why couldn't he have been patient and nice the whole time. Like sheesh, I know it wasn't smooth, perfect, and easy, but it could've gone a lot easier if they didn't assume I knew exactly what they wanted to do without being clear, and if they had of actually listened to what I said.