I intend for his thread to be a discussion of places where you expect to get barely tolerable food -- a convenience store, a mall food court, a tourist-trap chain -- only to discover something really chow worthy. One example, frequently mentioned on this board, is the Indian food served at the food court in the Burlington Mall, which is surprisingly good.
Here's my contribution to get us started: I have always found Starbuck's sandwiches to be above average as far as pre-wrapped sandwiches go, but still not chow worthy. And I find that you've got to wait half an hour to eat them after you buy them to get the chill of the refrigeration off. Today, however, I bought a tomato, basil and mozzarella sandwich on ciabatta, and I had them heat it up in one of those ovens they installed in many stores last year. It was GREAT, even after applying the got-it-at-Starbucks demerit.