For all cashiers and customer service reps, what is your biggest pet pet peeve with customers?

When I worked as a cashier I couldn't stand when people put all of their change and dollar bills on the counter and then pointed to it when I told them their total.

some really pissy people won't shut up about how their food is bagged. like i know how do to it, eggs on bottom, with light on top, boxes together,, bread & chips on top,, etc. but who cares if shampoo is with your crackers? UGHH

balling money up