QR Codes were all the rage a year or 2 ago. They got a lot of press, and everybody was experimenting with them. They caught on enough so that people are generally familiar with them now, but I'm not seeing a lot of good application. In a perfect world, here is where I'd like to see QR Codes used.
On anything that has to be assembled or connected
Within the last few months, we bought a harman kardon soundbar for our TV and a sprayer for the garden. The sprayer took me a little longer than it could have to assemble, and it would have been nice to be able to scan a code on the package and go to a video showing me how to assemble the thing. The soundbar was a bear to connect. There was no text on the instructions, obviously so they didn't have to be printed multiple times in many languages. But the visual instructions were really, really bad. Very little was obvious, and there was no way to clarify anything. So we checked online and found little clarification, and then we called harman kardon...3 times over the period of about as many hours. Wasted afternoon. Why didn't they just have a QR code on the box that linked to an online video that showed us how to complete this project and save 2.5+ hours of our time?
On anything that might require that parts be purchased in the future
Most people discard packaging after they unpack something, so in this instance, it would be wise to stamp the QR Code right on the item. That way, down the line, when I need to purchase a replacement part, I can just scan and link to a place online where I can order what I need.
On business cards
We all have our web addresses on our business cards, but why not make it a whole lot easier for someone to find you online? This could link to your website or perhaps your LinkedIn profile. If you make it easier for someone to check you out, without having to type your URL, you just might get a leg up on that job, project, deal, gig, etc.