Classic creepypasta. It's this one, the search and rescue stories, and I think there's another that slips my mind right now.
EDIT: boy did I miss a few.
- Ben Drowned
- Candle Cove
- Russian Sleep Experiment
- Squidward's Suicide
Of course, some of the weaker ones imo are also classics:
- slender man
- jeff
- the backrooms
Romeow