The listing, Paranautical Activity (PC, Steam) has ended.
Paranautical Activity is a brilliant indie rogue-like FPS. What does that mean? It's an old-school first person shooter (not too different from games like Doom or Serious Sam), but the levels, the item and monster placement are procedurally/randomly generated, making it that each playthrough becomes different. As you get through increasingly challenging rooms and boss fights, you level up and boost your character as well, and overall this game is a lot of fun. I played this game a lot personally, and it's really good!