I think these two movie horror-movie previews summarize two things I'm ridiculously afraid of.
Yes, I am freaking terrified at being stuck at the bottom of a cave. I don't know where this came from or why it scares me so much, but a deep dark unknown is terrifying.
(and I promise you I will never never NEVER ever ever see this movie (and it's rated R))
Here is a more recently developed one, probably because it's more long term:
And the other has been a realized fear, psycho roommates.