Something I could think of would be:

1. Buy the gift card with an FB Amex cc or other airline point yielding cc, somehow (I think very difficult to do in my country).
2. Use it to buy random stuff at a certain store
3. Go to another instance of that store (or just return to the same store a couple days later) and return the items, asking for cash
4. Rinse and repeat.

You'd have to buy A LOT of gift cards and A LOT of stuff for this to work though. And I am not sure if some gift cards have a maximum $ of stuff you can buy with them (will they accept that you buy something worth 100s of $ with a plethora of gift cards?