- Sonic the Hedgehog 2 contains data for a cut level called “Genocide City”
- Obscure Wolfenstein clone Corridor 7 randomly jumpscares the player with a red demon face during regular gameplay
- Dog Island, a Wii game in which all the characters are adorable chibi dogs, has a subplot about a doctor whose botched treatment caused the death of someone he loved many years ago. He still sees her in his dreams, unable to let go or move on.
In The Elder Scrolls IV: Oblivion, saving in Frostcrag Spire, quitting, uninstalling the Wizard’s Tower DLC, then loading the save dumps you in a debug cell the plugin overwrites which - among other things - connects to a completely unlit Oblivion tower. If you’re in a part of the wizard’s tower that doesn’t overlap with a in-bounds part of the debug map, you fall out of bounds when loading the file.
(In a decidedly un-scary note, you can retrieve a severely broken debug weapon and one of each sigil stone with every single effect while you’re in
BrumaTests)