I made a pretty business card for photographer with QR code on one side. It sounds like a good joke that you have to take pic of his card if you want him to contact you to take yours. I just feel like I don’t want to right anything more, so I illustrated how it works if you have card, cell phone and app that recognizes QR codes on that phone:

Just because I try to be honest every time it is possible (two or three times a year ;)) I want to confess that QR code on illustration doesn't represent contact information while it just contents known mem

I use QR app on my iPhone to recognize QR codes. It helped me a bit on Sziget ;) You can practice in recognizing codes using any QR codes in this post. Here is one more with my contacts:

Other unusual cards