When I first started looking for a career, COBOL was very common in banks and they recruited heavily for students just out of college (less than 20 years ago) and were willing to give them time to learn the language. As I understand it now, nearly all the COBOL is done at the mainframe/backend and the front-ends are all stuff like ASPs, JSPs, java, etc. I'm guessing the jobs are still there, just a lot less of them.
As for Ada, yeah, it was designed for and used by the US DOD and even required by them until 1997.
My personal rarely used language is Forth, which I learned to hack Open Firmware so I could make my mac boot either Yellow Dog Linux or OS X (installed on separate drives). That saved me a cable swap (boot ordering didn't work so well - the mac always wanted to format the unknown drive), but eventually I just started using XonX and not using the dual boot, and that was similar to my older setup that ran OS 8 on Linux (MacOnLinux). Been 10 years at least, so I doubt I could still program Forth without a refresher.