Monster Hunter Stories (3DS) QR Codes
Sourced from Reddit but I don't trust like that so I wanted to have an archive of my own should anything get taken down.
These all work, I tested them all today (one is a duplicate but I can't remember which). You do not need to connect to the Internet or Nintendo servers for these to work.
I might be missing some, I will be searching at some point to make sure this list is 100% complete.