Wikipedia says that the Dumpu (or Watifa/Watiwa) language is expected to be extinct in a few decades.
Part of me hopes that it will survive purely so that there will be more documents which can be language-tagged with its ISO 639-3 code.
I suppose similar things can be said about the Omagua/Omáwa dialect of Cocoma, which Wikipedia says is spoken only by two people near Iquitos in Peru, but which was originally spoken more widely in western Brazil.
(The Wikipedia article doesn’t list the ISO 639-3 code, but you can probably guess what it is. Similarly for the Bamali language of Cameroon, which doesn’t even have its own entry but is subsumed in the article on Nun languages. And if you really can’t guess, have a look at the IANA language subtag registry.)
Hm, the Mongo (Lomongo/Nkundo/Mongo-Nkundo) language also falls into this category, I suppose :)
Perhaps someone should start using those language names as codes for Internet abbreviations—for example, Solomon Islands Mono language for when you agree completely with somebody else. (Pity that "ikr" hasn’t been registered yet.) Or Imbo Ungu (Imbongu) for when you want to state your opinion, or Imraguen/Imeraguen when you’re talking about your experience.
(And now I wonder whether anyone worships the Godié language of central-western Côte d’Ivoire :D)