When I was younger, maybe around 12, I was alone at home with my sister who was 10 at the time. Our mum went down the road to a family friend's house. It was really late (past 10) and she was still not back. We were watching TV when suddenly someone hit the letterbox twice really hard and without looking we opened the door straight away (we assumed it was mum). When we opened it, there was no one at the door but in the middle of the road there was a lady just standing there staring at us. It was really dark so we didn't see the face or anything properly and then we just shut the door and sort of shit ourselves. Our mum came back around 20 or so minutes later but definitely one of the creepiest moments ever.
I have loads more but this would become a massive post if I carried on.
Edit: Another creepy story - probably creepier than my original post since I was getting scared typing it lol
So when I was about 7, maybe younger, I went to my mum's best friend's house with my mum in another city. It was just me, my mum and her friend and nobody else in the house. Except, when I was there, I saw a family which consisted of a mother, a teenage boy, a two younger girls that looked really burnt just walking around the house together without taking their eyes off me. At one point, they even told me to go with them. I didn't think anything of it at the point because I assumed they were house guests but many years later when I told my mum, she mentioned it to her best friend. Her best friend told her they had to move out of that house because they had many haunting experiences such as finding all her new baby's toys out in the middle of the night after she tidied it, things moved around and blankets and pillows on the floor as if people slept there. She asked her husband thinking maybe he did it but he was just as scared as her so they moved out.
TL;DR: I'm pretty sure I saw ghosts in my mum's best friends house.
Second edit: Another story or 2 - not as creepy
So I have these cousins who have always somehow lived in haunted houses. It probably makes more sense to say they're haunted. My uncle and aunty used to live in a small house first and they had just one child at that point and whenever they were downstairs, they'd here someone walking upstairs and whenever they were upstairs, they'd hear someone walking and doing things downstairs. They eventually moved and then at their third house, strange things happened too. Blankets would get pulled off when they're sleeping, you'd see family members walk into this this bedroom that no one stayed in but when you walk in, no one's there, it's just empty and this happened regularly. Then eventually, my aunty started going slightly crazy and said it was after she saw this scary ghostly woman standing in the hallway in their house. Eventually they moved out - there was a 3 girls and 1 boy and my aunty and uncle and the family they sold it to also had 3 boys and 1 girl, all around the same age.
The other creepy story is also about them but in their second house where one day their grandma was taking a nap in one of the bedrooms upstairs. My cousin, probably around 8 at the time went to her and she called her to take a nap with her but she just stared at her then ignored her and walked off to another room. Her grandma went to the room but couldn't find her so then went downstairs and asked her why she did that. My cousin and her mum replied saying she hasn't left the room for ages.