I-nigma is by far my favorite QR code reader for a mobile device. I'm sure there are others out there that work just as well, but I've been so satisfied with this one that I have no need to look elsewhere.
Here's what I love about this app -
1. It's free.
2. It scans a QR code quickly (I mean it's really fast). I barely get the phone in front of the code and it's scanned.
3. It keeps a history of all my scans. If I need to go back and look at something, I don't have to worry about where it is. I-nigma keeps track of it for me.
4. I can add any scan to my favorites. This way I can find things quickly.
5. I can share my scans through text message, another QR code, Facebook or Twitter.
I encourage you to take a look at I-nigma as your QR code reader. You won't be disappointed.