* DemonicSpiders: Due to the nature of the game mechanics, ''every'' enemy is one of these.
** The aliens themselves can charge you surprisingly fast; kill you in one quick hit, while they require a fully charged shot to get killed (and you can't run while charging a shot); and, most important of all, they're completely invisible. You can pick up a VPS detector that, through various beepings, can approximately tell you which side and how far away they are; the problems starts when it beeps without control because there's an entire swarm of the things around you...
** Larvae, on the other hand, are visible and can get killed with just an uncharged shot - and, by the time you find them, you have a gun with unlimited ammo. Now, the problem: the VPS doesn't work on them. This means that you're forced to use your regular sight (and larvae are quite small and hard to notice) and hearing (and larvae's noises only tell you if they're nearby, but not which side they're coming from). Oh, and if you don't notice them in time, they still kill you in one hit.
* SugarWiki/MostWonderfulSound: The horrific shriek of a dying alien would be horrifying if it wasn't such a damn relief.
* {{Narm}}: The otherwise chilling and well-made opening cutscene gets marred a bit by Parker letting out a very silly StockScream when he gets killed.
* NightmareFuel: While the invisible enemies, OneHitKill 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.
* RetroactiveRecognition: One of the animators for the game was someone know as Fumito Ueda. You know, he of the ''VideoGame/TeamIcoSeries''
* SerialNumbersFiledOff: The plot heavily borrows from ''Film/{{Alien}}''.
* ScrappyMechanic: Invisible enemies and single shot long charging weaponry in "Enemy Zero". Doesn't help that the whole game is made before 3D surround sound or it was made for a console that didn't support such feature. This time there ''is'' a save feature… an audio recorder with 64 charges; saving burns three charges… and ''loading a save'' burns one.
* SpiritualSuccessor: Got one in form of ''Videogame/NoSonOfMine'', as the newer game has a charge-based weaponry and beep-based threat indicator along with a nigh-invisible threat.
* TearJerker: [[spoiler:David's and Kimberly's deaths.]]
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