The Hunger Games (novel)/Nightmare Fuel

Books
""Are you, are you, coming to the tree... Wear a necklace of rope, side by side with me...""
 * The Games themselves are this. These books do not skimp on the terrifying deaths. There's also the effects of Tracker Jackers on Katniss (who survives) and the careers (some of whom don't), and  death.
 * Throwing teenagers into a death match is bad enough. But turning them into celebrities beforehand, putting them into social situations where they even eat with the people they will eventually kill or be killed by, and even forcing those from the same District to fight against each other, destroying any camaraderie or prior relationship they might have is just plain monstrous. And that's not even getting into what happens to the victors AFTER the Games.
 * death, where his
 * "Tick, tock." There is something deeply unsettling about the whole  idea.
 * The Hanging Tree song.


 * Katniss' explanation of the song doesn't help.

Films

 * When the mutts first appear in the arena in the movie.  One can only imagine if that was in 3D...
 * All the other incidents of violence -- the mutts, Thresh and Clove, Glimmer's death -- are all either really violent so as to be almost unbelievable, covered up with a Jittercam, or not particularly scary, like Rue's death by spear or Foxface's poisoning. The death of the District 3 boy is so senseless, happens so quickly and is done with such little emotion that it's shocking.
 * The Career tributes, Clove and Cato in particular. One of the most disturbing scenes is after Katniss's leg has been burned and she's soothing it in the lake. The disturbing part: They're glad that they're about to kill somebody. This is also Fridge Horror when you realize that these people probably reflect their districts.
 * The Tracker Jackers. Everything about them, from watching them swarm around Glimmer as she screams to Katniss's hallucinatory run from them, is terrifying.