Nightmare Fuel / Halo 3: ODST

• The story that the audio logs tell is much darker and more gruesome than the main storyline. This includes a corrupt cop Kinzler who tries to rape Sadie, massacre civilians, and send dozens of his men to their deaths just so he can secure the Engineer and become a hero. He eventually gets what he deserved, by being torn apart by an angry mob, still alive throughout the entire process.
• The Mombasa Streets level is quite eerie, especially with the moody music, being utterly depopulated except for the occasional Covenant patrol, with signs of the UNSC forces having fought tooth and nail against the Covenant for control of the city. The walls are littered with graffitis such as "Twilight of Man" or "We're next" highlighting how humanity is making a Last Stand against utter extinction. Up until Halo: Reach this was one of the most visceral way to show how horrifying a Hopeless War against genocidal Scary Dogmatic Aliens would be.
• The sight of the Covenant Carrier beginning to glass the city is enough to give a panic attack to Gunnery Sergeant Edward Buck, who was there on Reach when the same thing happened and barely survived to escape.