-Customers calling the store phone while they're inside the store so that they can ask the service rep where to find an item.
-Customers coming up to you while you're wearing a jacket, leaving the store, asking you if you can help them. Also, ones that see you obviously on break (three people at a table eating lunch) and ask for help. Usually prefaced with "I know you're on your break, but..."
-Customers complaining to Customer Service about the lines at the register. "Can't you open up more people?" Yeah sure lemme just pull a few extra employees out of my ass and open 'em up for ya lady
-People trying to get some lower price or abuse some mechanic and justifying it with "Well they let me do that last time!" I usually end up responding with "I don't know who did that last time, but they were wrong, sorry."
Then there's the people that insult the employees and call them uneducated, idiots, pain in the ass, etc. but that's not really a trope, that's just being a douche
--
http://img.imgcake.com/McBones/MvC3politicalupdatejpgyt.jpg