Seeing as we're telling stories of big bad consumers taking poor little corporation for a ride, I'll throw this story in NOTE: I don't necessarily condone this but it is funny.
Some friends of mine were renovating their basement and purchased about $600 in floating flooring from Home Depot. The day after they bought it the store put the flooring on promotion for 20% off so they went back with their receipt and asked for a discount, the store happily obliged and reimbursed their credit card for 20% of the purchase and provided a new receipt. The store didn't reclaim the original receipt so my friends went to another Home Depot and did it again, again they left with the original receipt. Naturally they drove 45 minutes to the next town over and did it again. Net result: $600 in flooring for $240. Not very honest but I doubt they'll see the gates of hell for it.
Reposted with bold text for clarity. When they told my wife and I this story we just shook our heads, these guys always pull stuff like this. Still think it's kinda funny, shady but funny.