What's the most annoying, time wasting thing that someone ahead of you in a checkout line has done? Here's mine:
The lady had picked up the small brown bags that the store places near the ice cream section, so that you can store frozen foods in it. Presumably so that the ice cream doesn't melt too badly while you are shopping.
Anyway, she had picked up these small brown bags and gone through the store putting 2-3 items in each bag. A chunk of cheese and deli meat in one. Yoghurt and granola bars in another. And so on. She had eight such bags and asked the clerk at the checkout counter to put the items back in the same bag. So the clerk was unpacking each of the ice cream bags, scannning the items and putting them back in. One bag at a time.
Since 100 brown lunch bags sell for $2, this woman was messing with all of us behind her in line for a lousy 16c. Never mind how ungreen it is to use brown paper bags (and I know she'd at least talk the green talk because of all that crunchy stuff she was buying).