Your nightmares.

[Grach]

I once had a horrible nightmare where I went to the university and found out I had to complete 3 assignments/essays for the next day, something I was unaware. I lost my shit.
Also, a very brief one but harrowing one, where I woke up and opened my room's door and found a masked killer, knife in hand, dressed only in a black fullbody spandex suit and a white mask with a horrifying smiley face painted in dried out blood. I just remember calling my brother in panic after that.

 

[TehCookie]

I'm a lucid dreamer so when I have nightmares I can change it to something more pleasant. The only dream I couldn't do that it was one where I was locked in a haunted house, and my friend had the exact same dream. That was creepier than the dream itself.