Hidden game gems, games that went under but are great, etc.

As the title states, I wanted to ask around a little who here knows some hidden game gems that are unknown.

I personally, contribute to this "list" (?) this game.
It is so unknown, that at the end of it's life I bought the boxed version at a German retailer for a euro.

It is a great RTS game. I returned to it after some years and a new 40€ expensive copy, started making a custom campaign for it (it has an editor with the "SAIL" programming language, which is essentially Pascal, since the game was programmed in delphi (I also know Delphi! Mahou right?).

Anyone who likes RTS should check it out.

Is there anyone who has the same feeling about some other game?