Forget all the mainstream crap that even the normies will rave about like it's the second coming. I want to know about the most obscure titles I've probably never heard of or are so old people don't even realise they exist but are actually all really good.
Three picks of mine that might have not made their way on peoples' radars.
https://www.anime-planet.com/anime/heavy-object
https://www.anime-planet.com/anime/jormungand
https://www.anime-planet.com/anime/tytania
I love serious sci-fi a lot or stuff that borders on it, bonus points if it's got good animation with proper battles, these three anime fit the bill for me. Jormungand is more of a military style anime but I often find these anime that fly under the radar often tend to be the better quality ones rather than the more heavily advertised mainstream titles and isekai trash.
That's the thing, perhaps this tells you how jaded I am but even an average space opera these days is great for watching. I liked Tytania, even though it was clearly low budget because they duplicated the ships to make their fleets they still had a more consistent design and storytelling than most stuff out there.
I've ranted about this before in regards to art anime studios put out, but there's isekai trash, which has at least acceptable levels of silliness with their art in it but still entertaining enough to watch through. Then there's isekai garbage where they spend most of their time designing oversized 3D monsters and low effort low FPS characters because they can't be bothered hand drawing anything in which case you should have gone and made it a full 3D scene so you had more to work with.
Tytania didn't do that with their stuff and the 3D worked because it was spaceships so it wasn't jarring when they switched to hand drawn scenes. I think I only caught them doing the old slideshow trick twice in the whole series.
That's just me looking at it from an art perspective though it's refreshing lol.