Saw this on cheap ass gamer. There's a coupon for $10 off XBox 360 that was scanned off a catalog that people have been printing off and using, which isn't supposed to be duplicated in the first place. Not only did he get the cashier to accept it, he got him to accept it for games that aren't even 360 games, and got him to STACK them. Look at the ridiculousness:
"My Target has the best employee ever. Grabbed a bunch of stuff, he grabbed my coupons and just started scanning. For $8 I got:
No More Heroes
Theme Park
House of the Dead 2 & 3
Devil May Cry 3
The Simpsons Game
Parappa the Rapper
Crazy Taxi: Fare Wars
Jeanne d'Arc
And about 15 various arcade download cards."

I count about $270 off due to ONE scanned coupon for a catalog.
http://www.cheapassgamer.com/forums/showthread.php?t=182349&page=27