Nightmare Fuel / Far Cry 3: Blood Dragon

• The Blood Dragons are actually pretty frightening the first time Rex meets them. After reviving to find himself in a cave, and trudges his way towards the entrance, only to find neon blue liquid running down from above onto the floor, staining it. After a few seconds, the top half of a cyborg soldier falls to the floor in front of Rex... and he looks up just in time to see a massive freakish reptile glaring down on him. And Rex can only crouch walk away from the Dragon through the grass, crossing through a valley full of them, and all he can do is throw cybernetic hearts to distract them, never once straightening up for fear of getting attacked.
• The setting itself can be pretty scary to explore despite the fact that the player character is a badass cyborg warrior. The island where the game takes places is perpetually shrouded in darkness under a stormy blood red sky with the primary sources of illumination being various eerie glowing neon lights that gives the whole place a dark atmosphere despite its overall Denser and Wackier tone. Even worse, a ruined burning cityscape is visible on the far horizon (likely as a result of the apocalyptic nuclear wars that took place in the backstory) that adds to the isolated and desolate feel of the island. And let's not even get started on the wildlife... from disfigured devil goats that look more like zombies than mutants and cyber predators with metallic bodies to the titular Blood Dragons themselves there are now even more nasty ways to meet an unfortunate end than there were in Far Cry 3. If not for the cheesy cool 80s action flick style the entire expansion is done in to soften the darker elements Blood Dragon would probably feel more like a tense Survival Horror than an action sandbox game.
• The effects of the dragon blood when ingested. On cyborgs, it supercharged them, making them nigh unstoppable. On regular humans, it turns them into the Running Dead; Mindless zombies who can only kill. Carlyle attempts a workaround by injecting himself with nanites. This has the effect of supercharging the nanites, which destroy his physical body.