This is based on opinion. Please don't list it on a work's trope example list.
Nightmare Fuel / National Lampoon's Vacation
The scene where Aunt Edna dies during their trip. Especially when they wrap her body up and put it on the roof, and then deposit it at her son's house. Granted, she was an insufferable old bitch, but it's still pretty morbid.
A Deleted Scene shows a Finger Twitching Revival while strapped to the roof, then left at her son's house. Apparently this was left out because it was darker than leaving her corpse outside her son's house.
Clark's breakdown speech. It's pretty jarring hearing such a happy-go-lucky guy in such an aggressive state of denial:
"I think you're all fucked in the head. We're ten hours from the fucking fun park and you want to bail out. Well I'll tell you something. This is no longer a vacation. It's a quest. It's a quest for fun. I'm gonna have fun, and you're gonna have fun... We're all gonna have so much fucking fun we're gonna need plastic surgery to remove our goddamn smiles! You'll be whistling 'Zip-A-Dee Doo-Dah' out of your assholes! I must be crazy! I'm on a pilgrimage to see a moose. Praise Marty Moose! Holy Shit!"