This is based on opinion. Please don't list it on a work's trope example list.
Nightmare Fuel / Sid Meierís Alpha Centauri
What can be scary with a Civilization-style 4X strategy game, you ask? Watch the cinematics for, say, Self-Aware Colony or Dream Twister Secret Projects.
"We must dissent..." from the Self-Aware colony was really chilling the first time, and it is still creepy It's basically the "Ubiquitous Law Enforcement" of Vernor Vinge's novels come to life. The cinematic shows two dissenters getting vaporized and all traces of them erased from the scene.
The sudden audio distortion in Zakharovs' speech for the Singularity Inductor is pretty disturbing. Hell, he's probably the single creepiest character in the game, far outstripping Yang. His clinical descriptions of his research often get very disturbing.
"I still have it, in fact. As you can see, the damage was not so great as they say..." — Prokhor Zakharov displaying the lab animal used in the first live teleportation experiment. Though, alternatively, it could have just meant that the rat is perfectly fine - or that the damage isn't visible on the outside...
And, though in a slightly different vein, The Cloning Vats. An almost cheerful description of how society will profit from thousands of clones of people who are the best at what they do, combined with video footage of chick sexers at work, ending in a shot showing several cute little baby chickens going down something that resembles a drain. Yeesh.
Not to mention all the graphic descriptions of what mind worms do to people.
"Richard Baxton piloted his Recon Rover into a fungal vortex and held off four waves of mind worms, saving an entire colony. We immediately purchased his identity manifests and repackaged him into the Recon Rover Rick character with a multi-tiered media campaign: televids, touchbooks, holos, psi-tours - the works. People need heroes. They don't need to know how he died clawing his eyes out, screaming for mercy. The real story would just hurt sales, and dampen the spirits of our customers." Mythology for Profit, Morgan Stellartots Keynote Speech
Made even worse by the near total silence - it's the only secret project video in the game without a voiceover (the text given above briefly unrolls on-screen at the end of the video).
The torture scene when you defeat a faction is a little disturbing.
When you realize exactly what Nerve Stapling is. Brrrr.note When strapped to a patient's head and upper back, the nerve stapler extrudes hair-fine probes into his brain and spinal column. A psychotherapist can then use the device to inflict extreme sensations (not necessarily pain) on the patient, subjecting him to a rapid course of psychological conditioning.
It matches the description of a Punishment Sphere according to the GURPS supplement. No wonder bases with them have their research halved and lose the ability of their citizens to become talents. Not only that, the GURPS supplement says that it is based on nerve stapling, but instead of performing it every few hours, it does it around every five minutes.
One disturbing implication if you're playing as Cha Dawn is that if their attempt at Transcendence somehow fails then it is a sign that Planet is rejecting humanity. As far as the Cult is concerned, humanity has already ruined one planet and clearly isn't worthy of living with this one, so the plan becomes wipe out every other human faction on Planet and then commit mass suicide. Yikes.