I had an opportunity to preview an early access build of DUSK. The short preview article is here on GameSpace: https://www.gamespace.com/featured/dusk-early-access-review-fast-fun-brutal-mayhem/
You can find the game on Steam here: http://store.steampowered.com/app/519860/DUSK/
I'm not even going to try and not fanboy over this game. It pretty much does everything right, from character speed, background music, gun choice and play, clever map design, multiplayer, and most all the trappings of the great nineties shooters. It offers a three chapter campaign, an endless onslaught mode, and multiplayer. Additionally, it offers mod support (and they provide game assets for that), including support for some other mod formats. Finally, when the game is completely finished they will open source the engine (not their assets) so anyone can make their own game complete with custom assets and music.
It truly is an Early Access title in that the third chapter isn't and modding tools aren't complete. They're also working on performance and polish. The game runs smooth on my 4790 with a GTX970.
Have you played it? Are you interested in fast-play brutal shooters? Check this out.