I hate when you pay for something, and you hand the cashier your credit card, and they swipe the card and then put it on the counter instead of handing it back to you. If I hand you something that's mine, for temporary use, you hand it back to me. You don't put it down on an other-people's-filth-encrusted, wet, sticky counter top. That's just rude! Next we'll work on eye contact and saying "you're welcome."