I sometimes get caught between dreaming and wakefulness and it used to be a bit scary. I am way better than I used to be, my husband is very grateful for that. I believe it is called parasomnia.
One night I "woke" and saw a big gun on a tripod in our hallway, pointing at our bed. I was terrified, convinced it was real and that if we moved a trip wire would set it off. I woke hubby up and said "there's a gun, you have to roll out of bed onto the floor and crawl to it to turn it off". He was half asleep and actually rolled out of bed onto the floor. At that point, I woke up fully and said "oh, never mind". LOL! That is just one instance.
One of the scariest dreams I remember having was when I was in my early 20s and was living alone for the first time in my life.
I “woke up” from a bad dream and looked into the doorway to my bedroom and saw the Grim Reaper. Yes, the stereotypical Grim Reaper with no face and a dark cloak.
Terrified, I then actually woke up. I was physically sweating and shaking for many minutes after waking with my heart racing. It was only a brief moment with an image in the dream, but it had instantly put my entire body into a very real state of panic.
On a somewhat funnier note (though not at the time), my dad attacked me in the middle of the night when we were in a hotel room. He is a terrible snorer (though he doesn’t believe he is because he hasn’t slept next to anyone for around 30 years) so I went out to the car to grab my noise canceling headphones.
I made it out the hotel door without him waking up, but as I was getting back into my bed once I returned, he jumped out of his bed saying “what the FUUUCCCK” and lunged at me. He seemed to wake up halfway through his lunge. For however many seconds, he was fully convinced he was at home and I was an intruder who had broken into his house.