As many of us pass through various airports and cities around the world, e.g., NRT or HKG or LHR, I thought it would be useful to have recommendations on acquiring certain specific products while there.

For example, I shall pass through NRT in two days. Any highly recommended gadgets for which a transit through NRT represents a special or even unique opportunity?

If this thread takes off, as I hope it will, I'd volunteer to maintain it and keep the recommendations summarized in the first post. Please specify if your recommendation refers to the airport or involves venturing into the city.