Latin

Latin is a curious language, no one grows up a native speaker of this ancient language, yet it can be heard all over the world. If one knows where to look. Once it was the universal language of the Roman Empire and the European states that replaced it. Then it was the language of learning and diplomacy. Now it is the language of the mass as celebrated by Roman Rite Catholics and little else. It can still be heard in the Vatican and Pontifical Universities of Rome; but even there Italian is often used as a language of convenience, to the frustration of the international community there.
For all its apparent irrelevancy in the modern world. Latin still holds a surprising degree of usefulness. Not only in direct readings of intellectual greats from ancient Romans to early Moderns. It's lack of native speakers mean all must learn it as a second language, and enduring such an experience forms a rare kind of bond between men. It also ensures that no nationality has an advantage in communication within the Holy See. Something seen as important in an institution as international as the Church, but dominated at it's highest level by Italians. Though given the recently fractured nature of the Italian peninsula, this may not be as much of a concern as it might be. Especially given the infamously quarrelsome nature of that people.
An anachronism it may be considered by the modernists of the world, yet by its very nature as an ancient, enduring and therefore, unchangeable language, a very useful feature in translation given how the meaning of words in other languages change over time. One may have a gay old time with that problem. it also possesses a majesty and force, especially when used in prayer and liturgy, that few other languages can claim. Perhaps because it the inherent mystery in a language most cannot speak or, perhaps, it is because as some claim; the devil hates Latin.