What languages did you have in mind?
Cornish? I would admire anyone with that amount of local patriotism
Irish Gaelic? I would rather the IRA (Provo, Continuity, Real, whatever) prefered to assert themselves linguistically than by trying to blow me up! (I am old enough to remember their mainland campaign of August 1939).
Latin? I do not think anyone is trying to revive it, just know enough to read, and understand it and appreciate its wonderful literature.
British English? It has been dying ever since they invented the Talkies, and no one has the strength, the patriotism or the obstinacy to work to save it. 'Tis a poor thing, but mine own. À bas les américains!
Quebecois? I think it will outlast us all. I only wish they could be as concerned to conserve French cuisine as they are to conserve their version of the French language.
Friesian? While English, well American English, conquers the world, our closest little sister hovers along the North Sea coast of Germany and Holland on the very brink of extinction. It is just not fair!
Timor Portuguese? Barely clinging to life, after the invading Indonesias shot anyone using it, it survived only among the guerrillas in the jungle, and now they have come out into freedom and victory, they have a whole nation to persuade to revive it. By why not? Failure would mean that the unspeakable Indonesians had won after all.