Overload
>a 6DoF FPS with actually good complex old-school level design filled with secrets and non-linear progression, has a campaign of 15 large levels
>intelligent enemy AI capable of dodging your shots and leading theirs, on top of being able to respond to your flashlight
>runs on Unity Engine, but is actually well-optimized
>loads of different enemy types with unique behaviors
>comes with a level editor and video tutorials by the developers on how to use it
>has an available demo on the developers' site, but very little people know because it's not actually called a demo but a Playable Teaser, and is not made clear as one on Steam where you can usually tie demos to your games for everyone to see
>jammin' soundtrack
>features an upgrade system with upgrade points you need to find by finding them in secrets, but it's actually worth a damn because per every second weapon upgrade you have to make a binary choice between two options which locks out the other
>non-intrusive storyline, can almost entirely be disabled
>new game+ mode adds new enemy placements to every level, most of these enemies only ever appearing late into the game
>basically Descent 4, but with a lot of refinements to make it less bullshit and less trial 'n error
>has a working multiplayer, though it's match-making only and very little people play it
If you consider the actual output of FPS games in the past decade, Overload is easily the best.