We had this a couple weeks ago at the office I work at. On mondays everybody on my floor gets together to plan the week ahead. We have a big A1 paper hanging on the wall and we use post-it notes to fill our activitiets in so that other colleagues know what everybody is doing.

So anyways, we all put our post-it notes on the days and after that we discuss a little. While we are discussing we hear a loud bang and suddenly every single post-it note falls off of the paper. These were new stickers and if you have ever used one, they stick pretty good to any surface. There were more than 50 post-it notes on there and they were all on the floor.

Multiple people were convinced it was paranormal, others think it was the loud bang that caused it. We still to this day don't know what caused the noise. It is a fairly quiet street.