In my Books, Gosick is not that obscure, it was super popular for the moment it was and then fell there.
I would say same, but much more sad that Space Dandy is in same boat, that hing is a master piece and it's OST is superb.
Now... I have few decades of nerdy like for anime behind me and depending on person some of these might not be very obscure at all but still recommending them. These are even in my estimation more "kinda obscure"
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Kino's Journey 2003 (not you Remake/Continuation season, you are very mediocre especially in comparison)
Extremely good for opening up philosophical concepts and questions to people not so primed for them, and extremely unique setting for making these short stories of philosophical musing. The visuals and music especially underline the beauty and lack of it.
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Mushi-Shi
Also a very story-of-the-episode structured show with muted atmosphere and interesting concepts for life values and philosophies underlined by slight super-natural nature to the world.
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Patlabor
Especially the movie trilogy
Likely overshadowed by works like Akira, this is one great series of movies that makes even non-mecha fans appreciate the "genre" for enriching the narratives with semi-futuristic mystery solving, political strong-arming and philosophies of different characters. I cannot recommend the TV anime, because I have not seen it, and it's very different, apparently entirely disconnected from the movies. I can unrecommend the live action movie though.