Please don't list this on a work's page as a trope. Examples can go on the work's YMMV tab.
Nightmare Fuel: The Happening
For all the movie's problems, there are a few genuinely creepy/horrific scenes.
The phone call where we hear a young girl afraid and confused about what's happening, and then jumps out the window because there was a tree near it — all as her mother tries to communicate with her and tell her to close her window. Everything else can be accepted as regular horror movie gore, but damn it, that is unsettling.
The old woman walking around the outside of the house and smashing her head against it, finally crashing in through the window. Gahhh.
The very concept is very disturbing. Imagine you are walking down a street in a busy city, and it's just an ordinary day. Imagine everyone around you, including yourself, just stops in their tracks, and then for no reason, they just commit suicide in anyway they can. You don't know why, you don't know how, and if you get infected, there is nothing you can do to stop yourself from killing yourself.
After splitting into two groups, Elliot's group watches as the larger group is affected, and gets to hear them commit suicide one by one with the soldier's sidearm. Even the hippie couple that had helped them out earlier.