This is based on opinion. Please don't list it on a work's trope example list.
Nightmare Fuel / Howard the Duck
As Dr. Jennings flees with Howard's girl, he begins to run out of energy. The way he recharges sent an entire room of birthday children running screaming, and a pair of parents regretting they had rented the film. Witness it here.
The possessed Dr. Jennings, and the horrid aliens, creep out any kid. ANYONE.
The scene where the bikers nearly chop Howard's head off.
When Beverly is poking through Howard's wallet, seeing the condom he carries, and recalling that ducks have giant, corkscrew-shaped penises...