J.C.
Around here, many of the grocery stores that have gas stations along with them sell gift cards at full face value, but you get points on the store points card for money off of gas, so say you buy a $25 gift card, you will get 10c off per gallon. This can add up quickly, and you can even put the points together at some of the stores. Two years ago, my ex got TWO fill-ups for 10c per gallon because he had so many points!
This isn't exactly what you were asking about, but I've never heard of something like you asked about, but this is a great way to get something back when you buy gift cards...When I need to do home improvements, I always go buy a gift card for home depot for around the amount I know I'm going to spend, and then I save money on gas later!