The usefulness of QR codes is still up in the air, but drinking a glass of Guinness is a ritual that has been around for hundreds of years. Winner of a John Caples International Marketing Award, advertising agency BBDO's cup reveals a QR code when filled with the Irish stout — lighter colored beverages need not apply as the darker tint is required for readability. Once the liquid is up to the brim, the code can be scanned to download exclusive Guinness content and promotions and even send notifications about your pint to Twitter, Facebook, and Foursquare. The glasses were distributed in limited supply as part of a marketing campaign; widespread availability has yet to be announced.