I've surprised myself with how many anime series I've recognised from this thread. Not that I've seen all the series whose names I'm familiar with, but I do seem to be aware of a fair few series people consider obscure. Maybe I should renew my otaku membership card >.>
As to the most obscure series that I've seen, ranking up there would be Great Detectives Poirot and Marple, an anime series adapting a bunch of classic Agatha Christie mysteries. Another would be FLAG, a series I only ever saw four fansubbed episodes of, which I consider one of the best/most interesting series I've ever seen. It's told mostly from the point of a war correspondent following a UN peacekeeper unit in a country that's just undergone a revolution, and a lot of the series is shown through a camera's viewfinder - a really interesting stylistic choice.
Bleh, this is getting a bit tl;dr, so I'll just add Tactical Roar, Soukou no Strain and Kishin Taisen Gigantic Formula as other really good series I've seen that are a bit off the mainstream track.
As to the most obscure series that I've seen, ranking up there would be Great Detectives Poirot and Marple, an anime series adapting a bunch of classic Agatha Christie mysteries. Another would be FLAG, a series I only ever saw four fansubbed episodes of, which I consider one of the best/most interesting series I've ever seen. It's told mostly from the point of a war correspondent following a UN peacekeeper unit in a country that's just undergone a revolution, and a lot of the series is shown through a camera's viewfinder - a really interesting stylistic choice.
Bleh, this is getting a bit tl;dr, so I'll just add Tactical Roar, Soukou no Strain and Kishin Taisen Gigantic Formula as other really good series I've seen that are a bit off the mainstream track.