When I was about 17 years old we lived in a basement flat in a tenement building. There was also a lower basement flat below us that my mum's friend lived in. She lived there with her husband and 3 sons. Her eldest son was about 20 at the time, and for years he'd suffered from paranoid schizophrenia. He was always getting into fights at bars, and he'd actually nearly killed a man when he'd stabbed him with a bottle. He didn't do time for it as he wasn't caught but his mum had told my mum of the crime and my mum had just stayed silent about it because it was her friend's son and she didn't want to get involved (wouldn't be my choice but I understood my mum wanting to stay out of it).
Anyway, eldest son also had a crush on me. He had done for years at this point and it really freaked me out.
So this one night I'm lying in my bed. My bedroom had glass patio doors which led into the back garden we shared with his family. I'm just lying there trying to sleep and the movement sensor light turns on, indicating there is someone/thing near the back door. I figured maybe it was just a cat or something. The next thing, there's some gentle tapping on the glass and the eldest son starts saying my name over and over and asking me to let him in, whilst pulling the handle down and shaking the door to try to open it several times. I was absolutely frozen to the spot. Then he starts counting down from 10 and I'm panicking at what will happen when he gets to 0. I can see his outline standing there behind the drapes as I'm lying there terrified in my bed, unable to to move.
Thankfully, after counting down he just said he was leaving and he'd be off now. I heard him leave, still counting as he went.