I'm a cashier at a big box store, and the thing that gets under my skin the most is when people who are buying a basket/storage tub/whatever PUT THEIR OTHER ITEMS IN IT AND THEN SET THE WHOLE THING ON THE BELT. Like. You're standing there waiting in line, and you couldn't take your damn items out so I can scan them? Bonus points if they're like 'oh, I don't need a bag, just put it all in the tub'. I've adopted the (sorta petty) habit of removing everything slowly while staring at them.