You know that wont work, and you will most likely get thrown out of the store if trying to use it. Its an old scam with new dates, ive seen it about 100 times already.
I'd try it out, but there's only one Best Buy store around here (far, far away), and I doubt it works on PC games. Of course, were I to use it, I'd be sure to modify it so that it says $25 off.