The creepiest thing that ever happened to me occurred when I was 12 and a devout Pentecostal. I had a friend with serious psychological issues and was very close to her, as well as her mother, who was religious to the point of mental illness. I really can’t emphasize enough how messed up this family was.
In essence, I spent years under the impression that I had exorcised a demon from my best friend. The conversation was heavy that night because my friend was suicidal. I don’t really understand what happened that night to this day, but I remember that her mother was reading a quote from the Bible about the value of life, and we were listening to Christian radio, and the man said something like, “'I sense a young person out there considering taking her own life…” Then he proceeded to quote the same Bible verse my friend’s Mom had just finished reading.
Naturally my friend’s mother freaked out. We were sitting at the table praying, and what I understood to be the Holy Spirit came over me, and I started shaking out of control. I ended up hitting my head on the table (not hard.) I had the worst feeling come over me, a sense of foreboding that I cannot describe, and then my friend walked into the bathroom and started convulsing. In retrospect, this was probably either a seizure or she just wanted attention from her mother, but at the time her mother and I both understood it to be the presence of evil.
Her mother started praying over her in tongues, and then the dog and cat started fighting (the dog was barking for no apparent reason), and I stood up and started praying aloud. ‘‘Get thee behind me Satan’’ and all that. My friend was unconscious on the floor, but when I laid my hands on her, her body was twitching.
Eventually she came around and claimed to remember nothing. We were so utterly terrified that we ended up sleeping on the kitchen floor that night.
In retrospect I can think of many possible alternatives to demon possession - the girl was seriously disturbed, and there were so many crazy things going on in my life at the time that I was probably in a highly suggestible state of mind. But at the time, I was scared out of my mind, and spent the next year or so sensing evil everywhere and feeling like I had to constantly fight it off. My Mom pulled me out of that church eventually and I settled down and became a fairly normal Baptist for the rest of high school. But even today, as an atheist, the idea of hell and demons scares the everliving crap out of me.
But yeah. Definitely the creepiest thing that ever happened to me.