Came in to say American Sign Language. 
Finnish. Well, it’s fairly obscure. I also studied Latin and Russian, but I can’t claim to speak them. Come to think of it, I don’t really speak Finnish any more.
Tibetan - there’s a tibetan students hostel where I live for students who study in Delhi university.
I would say “Tashi dele” (Common greeting like “hello” in Tibetan, means something like “Things be Auspicious”) to Tibeti student, they get confused, most reply back with “tashi dele” and a smile.
Some more:
“Khe rang kusu debo yin pe” for “how are you?”
*“Thu-chi che” *- “thank you”
One can easily pick up Tibeti girls like that.
I took Latin. I can speak Bill Cosby at the dentist. I’m learning how to write backwards with my last hand. I used to know Drac.
Every time I finish a project, I sign up for Basque lessons at my local Official Language School. So far, every time I’ve had to sign off before the classes even started due to getting a new project. Nowadays both are done via internet, so it’s much less of a pain than when you had to go in person.
I understand quite a lot (enough that using it as “Navajo code” won’t work) and can point out some grammatical features such as the most basic declensions but don’t actually speak it. My native Spanish dialect includes many words which are Basque in origin and which are rarely if ever used in other dialects.
SQL - Structured Query Language. I’m very good at it.
Took Latin in high school. No good at it.
Lived in New Mexico for 4 years and picked up a tiny bit of Spanish.
I follow professional cycling so about the only thing I know about the Basque is the Euskaltel Euskadi cycling team.
I don’t speak any unusual languages, nor do I have any interest in learning to speak them, which is odd because I do have a strong affinity for learning languages, of which I am most proficient in English, Spanish, and Japanese, in that order.
My German, which I learned and was conversational in as a kid, has fallen into complete disuse and I am beginning to forget it. My French is weak but passable, but that is only because I still use it from time to time. I’ve forgotten much of the Hebrew I learned and can now speak the simplest of phrases only.
The above stated, I am primarily interested in the etymology of languages and their interconnections. I am fascinated with how languages develop and change over time. The English language is amazing in that regard.
I’m actively working on my Romanian (language number 7) and not-really-but-want-to on my Welsh (would be 8). Neither is particularly obscure, but there don’t seem to be many people learning those languages. Finding a good textbook & grammar is a pain, and there are never classes anywhere or anyone to speak to.
If anyone is working on their Dutch & has the same problem, I’ll exchange emails if you want! 
My girlfriend and I have discussed learning Irish together.
My own ancestral languages include Yiddish and Hebrew, but those aren’t as useful for talking about people on the subway.
I speak English, Serbian, and 8 different Romany dialects. I am currently studying Yenish, a Romany dialect that was heavily mixed with Yiddish as part of my efforts to record as much as the Yenish speaking Roma history as possible.
I speak English, can get by in South American Spanish and am (slowly) learning Haitian Creole. Rosetta Stone doesn’t even offer the latter!
Once, for a very brief period, I had a passionate desire to learn Old Church Slavonic, which died out in the 11th century. Looking back on it now I can’t imagine why.
All my other foreign language dabblings have been thoroughly conventional.
Latvian. Enough French to get around in a French-speaking country easily.
Quail.
this is why i don’t speak russian too often. i know more church slavonic than russian, and you do get some odd looks. even from those who go to church!