This happened about 4 years ago. I was sharing a house with a friend and her two teenage daughters. There was a lot of ghostly activity at this house. For example, if you had a shower at night the light in the bathroom would always turn off, things would spontaneously fall off benches, things like that.
The house was made of bricks and the windows were high up, impossible to reach without a ladder.
One afternoon the youngest daughter asked me if I had seen the movie called Candy Man. In the movie if you look into a mirror and say candy man three times the 'candy man' appears and does bad things. Anyway the daughter asked me if I would look into a mirror and say candy man three times, which I would not.
These girls loved playing practical jokes, and I heard them whispering to each other. Then the youngest came into the kitchen, where I was, and asked me to say candy man into the mirror. I wouldn't so she said "Just say it once." I was aware that the eldest daughter was in the adjoining hallway so I knew one of their tricks was about to happen. So to make them happy I said candy man into the mirror once. Instantly their was a banging noise. The eldest daughter came into the kitchen, looking terrified and said "That wasn't me". She had tears in her eyes and had gone pale. I decided to play it down and told them not to worry about it and went about my business.
The girls wouldn't calm down and wanted all of us to hold hands and say "You are not welcomed in this house." So we did, almost as soon as we said this there was three loud bangs on the wall, very loud and so violent it made the window panes shake.
We had three dogs out the back and during this they didn't bark, which ruled out anybody outside doing this. And being a brick house, no human could bang on it that hard (we tried at a later date).
So anyway, all three of us panicked, we ran outside and just stared at each other crying, then we prayed. Needless to say, we never said the word candy man in that house again.