Country and Country Subdivision Unique Identifiers
Suppose you need the equivalent of GNIS' Feature ID for geographies in countries beyond the US. ISO maintains such a dataset. While its multi-national coverage means that its unique identifier is not neat and clean like the integer-valued Feature ID in the GNIS file, it does nevertheless provide a comprehensive and standardized key set - not to mention standardized geographic names and spellings, plus the organizational hierarchy.
Take Kigali, the capital city of Rwanda. For Rwanda, the official ISO Code is RW (or RWA using the 3 character option), and for the capital city, the code simply is RW-01. For another example, in Spain the autonomous community of Aragon is identified by the code, ES-AR.
Wikipedia is an alternative, albeit unofficial, source. Point your browser to http://en.wikipedia.org/wiki/ISO_3166-2. Of course, you will not find a structured, formatted file covering the entire planet. Plus you might not find codes for the lowest level subdivision. Still, if you need just a few countries and top level subdivisions, the Wiki site at least gets you started.