I would very much like it if when you make a purchase at a major retailer, the information on the receipt could be contained in a QR code. Though, to be honest I'm not sure that amount of information can be contained in a QR code.
If a QR code can contain that amount of information, one would be able to scan the QR code on the receipt for import into personal financial software, such as is available at mint.com. Rather than defining transactions by store (i.e. Safeway = Groceries), doing so would allow the financial software to know that of the $40 you spent on "Groceries", $8.99 was actually dog food (pet supplies), $7.99 was laundry detergent (household items), and the rest was food (Groceries).