These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
YMMV: Enemy Zero
Demonic Spiders: Due to the nature of the game mechanics, every enemy is one of these.
Hell Is That Noise: Ping...ping...ping...ping...ping ping ping ping ping pingpingpingpingpingpingpipipipipipipipipppppppppppp
Most Wonderful Sound: The horrific shriek of a dying alien would be horrifying if it wasn't such a damn relief.
Nightmare Fuel: While the invisible enemies, One-Hit Kill nature of the protagonist, and extremely limited range of any weapons can be annoying, one can't deny that they also make any alien encounters scary as hell.