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 Wicker Man
The islanders dancing about the Wicker Man, joyously singing "Summer is i'coming in" while Howie burns to death, howling in agony.
Also, there's something about the islanders wearing those animal masks that just isn't right. It doesn't help that the masks are very realistic. Or the way they just appear, and stare at Howie...
Despite the Narmy performance of Nicolas Cage, getting a mask filled with angry bees stinging your face is a horrifying thought.
You can replace the 'angry bees' with any other creatures that you have a phobia or allergy for (e.g: Spiders, snakes, scorpions, rats, worms, etc) in that mask and it's STILL a very horrifying thought. Compare to the infamous Ceti Eel scene from Star Trek II: The Wrath of Khan.