I've had two very terrifying nightmares, that I never want to have again, when I was younger. The first, when I was about 4, I was dreaming that I was laughing uncontrollably. Just constantly, seemingly forever laughing out loud, standing in absolutely nothing. I fell asleep while I was in a car while riding home from a 2 hour trip with my father. He wakes me up to tell me we were home, I get out of the car, and then begin laughing for no reason. This laughing, like the dream I had not even minutes before, continues on for a few minutes. I then began to freak out about it, for some reason not having the ability to stop laughing, and I cried out for my father and he didn't know what the hell to do. What I assume was about 10-15 minutes later I finally just stopped. It was terrifying. I had no idea, to this day, what had caused me to laugh uncontrollably. I don't remember anything funny happening, only that I dreamt about the same thing moments before.
The second nightmare wasn't nearly as odd, but still something I didn't like. I was in a grocery store, trying to run away from these gang of men in suits shooting guns at me. Some of the shots actually hit me in the dream, and they hurt! Incredibly. And I've never been shot before. (this was combined with that incredibly annoying instance where you try to run, but you feel heavy and you go almost nowhere) Eventually I woke up with my arms in pain where I was shot, but it quickly went away.