I was looking for single-use tags, and approximately half of our tags on Travel-SE (10 pages of them) are actually used once or are synonyms, so this is almost an exercise in futility.
To make it more clear:
Is there a way to exclude the synonym tags when browsing? Alternatively, is there a way to do this from the Stack API? I think we have a person or two here that can work with this (hi Roflcoptr!).