It is so impressive to see, how far the Doom engine has come if you take a closer look at Membrane, a standalone game developed by SuperDon which is based on GZDoom. Featuring fast gameplay, expansive labyrinthine levels, with fun sci fi weapons and powers. Membrane is a throwback to classic First Person Shooters, inspired by the likes of Jedi Knight, Duke Nukem 3d, and of course Doom.
The story so far: You awaken in the crumbling ruins of a laboratory. An alien membrane covers your arms and back. You hear it in your head... responding to your thoughts, telling you to escape! As you climb into the light, it becomes clear you have been the subject of alien experimentation. You can hear a patrol in the distance... you will have to fight your way out and find a way back to Earth! A gameplay trailer can be found in the official thread over at ZDoom as well es on the ModDB page.