Mine's a little odd, to me at least.
I fear waking up and realizing that I'm alone in the whole *whatever*, finding out that nothing ever really existed: My family, friends, this world, ideals, even my physical self. Sometimes I overimagine things, if a person leaves my room, is he non-existent therefore? Is there really a world outside my view or does it exist only when I see, feel, hear or touch it?
I hate those existentialist/nihilism classes.
Now, that's me. What about you guys?