Sending them back is nifty but how about collecting them then forwarding them to your bitter enemy?
I do like that idea about decorating the Xmas tree with them. Makes something unneeded and unwanted into someting pretty. OOOOO or how about breaking them down and making mosaics? I hate to mention the bride of Satan, Martha, but didn't she do a comercial way back where she was cutting up her credit cards to make a picture for her pool?