Just looking at the title, I thought ancient as in Amiga, ancient as in System/370, or ancient as in Antikythera mechanism?
Turns out to be the first two rather than the last, but there's an analog computer that, while much newer than Antikythera, predates all of these and is still in wide use today: the E6B Flight Computor, a sort of slide rule used by pilots to do time, distance, speed, and fuel consumption calculations and wind triangulation. Some pilots use digital versions of this tool but the old circular slide rule is still preferred by many because it doesn't require batteries and the pilot is used to manipulating the physical dials.
https://en.m.wikipedia.org/wiki/E6B
