We have, in my line of work, what I call the Haggling Herd, or the Coupon Clan.
Not one, but a whole gaggle of them come in, because they know that our policy is to allow only ONE coupon per person, per transaction, per day. That means NO, you cannot walk out of the store and walk right back in and use another coupon. That means, NO, you cannot use two coupons on the same item. It does not mean you can break your transaction into fifty, and use one coupon on each thing. If we wanted everything to be 40% off, we'd just advertise everything at 40% off.
So, to circumvent this inconvenience, they bring in their entire clan. They mill about and pull everything off the shelves. They leave wreckage wherever they go. They shout at one another across the store. They let their hellspawn (tired and hungry and bored) run rampant through the premises. They form a line long enough to make you think you're waiting for tickets to a sold out Lady Gaga concert.
Then they gripe that the ONLY person behind the cutting counter on the fabric half of the store is too slow and that the line is too long. They ask if every bolt of fabric is on sale. They ask if they can use a coupon. If the price is more than $2 they leave it behind. Most likely piled on the floor somewhere, where their progeny has decided to pretend the fabric bolts are surf-boards. Or building blocks. They ask for discounts because something is dirty. There's a single thread pulled at an edge that's going to get cut off anyway. They tell us they got it for a dollar somewhere else.
Once they're done assaulting the Fabric Counter, they all shuffle in a great, destructive migration to the register, where they begin their assault anew, upon the cashier. Somehow, they seem to think the cashier's answer will be different than the one the fabric counter gave them. Imagine their dismay when it's the same answer! They start a fuss. They bark and yell and carry on like a pack of furious chihuahuas. And then don't buy anything.
Or more frequently, they spend the $100 dollars on clearance fabrics, then return three days later with the stuff smelling like curry, stained and wrinkled - and attempt to return it all. And unfortunately, Malignant Management, forces us to do it.
Now the Coupon Clan attempts to get back more than they spent. Claiming mistakes, or that they didn't get the discount they were supposed to. Our computer (Which is benevolent and has no prejudgement) is wrong. So, in the long run, Malignant Management decides to just not argue with the Clan, and we end up PAYING THEM TO LEAVE.
Which only encourages them to return to do it again a week later.
Then there are the Illiterates. The custys who couldn't read a sign, now matter how clear the Sale sign is, or how specific the description - or how far from the product they have in their hand the actual sale sign is. The Illiterates are an entirely different breed, but that's another story for another day.