This is based on opinion. Please don't list it on a work's trope example list.
Nightmare Fuel / Hamtaro: Ham-Ham Heartbreak
An in-universe example at the beginning. In the opening cut scene, Hamtaro dreams of Spat destroying relationships in Fun Land. Then, from Hamtaro's perspective, Spat charges toward him until his face fills the entire screen! Hamtaro flies into nothingness until he is woken up by Boss.
Many scary moments in Boo Manor, a mansion full of ghosts.
If you make Hamtaro run over a rug in one of the rooms, he suddenly flies into the air. It looks like a ghost got him but he just tripped on sunflower seeds hidden under the rug.
Dexter getting locked in a coffin. And when the coffin's empty, if you Hif-Hif in front of it, the text box states that something smells old. Bijou and Hamtaro will look horrified before realizing they were actually smelling the roses around the coffin. If you Hamha while the coffin is closed, Bijou will say, "Actually, you know, I don't think I really want a reply."
The final room with all the creepy dolls. Even worse, one of them turns out to be Spat!
The bees which you NEED to upset to progress. The first time, they'll get Spat for you, but if you come back and disturb them again, they'll chase YOU. Cue Hamtaro running to the next screen, where thankfully the bees won't follow.