A few examples come to mind: geographic regions that already have codes or abbreviations associated with them (e.g. a FIPS code or state abbreviation in the US)

A few examples come to mind: geographic regions that already have codes or abbreviations associated with them (e.g. a FIPS code or state abbreviation in the US), simple enums (though I really only bother putting these in a table if they’re used in multiple places). Have to be careful using a string as the clustered index of a large table, though. Smaller tables with shorter string keys that experience very few writes are most ideal for these cases.