My two biggest issues when I work the register.
I constantly have people coming up to my counter wanting to check out or make a return and they’ll stand ridiculously far away from the register.
And snapping. I hate it when people snap at me.
I am there to help you, not to serve you. You snap at me, you will have my bad thoughts raining down upon you for the rest of the day or possibly week, depending on my mood.