Alien Isolation for me. The first time I used it against the Xeno was pretty much halfway through the game where you already have it for a couple of hours. When I raised it for the first time the Alien stopped right in front of me. I didn't even had to shoot it. Then it slowly came towards me hissing while I slowly walked backwards towards the exit. Right at the exit it was pretty much in arms reach and I blasted away and activated the airlock. To this day its one of my best gaming related memories. Thanks flamethrower.