I posted this elsewhere but this thread seems appropriate.
I used to live in an apartment that was once the emergency department of a hospital. (the whole complex was an old hospital) I didn't really have any beliefs about the paranormal before I moved in, and I was forced to reconsider after living there.
There were lots of little things. Hearing footsteps but nobody being there, bangs and knocks in the night, and our bedroom door often opened by itself while we were trying to sleep. You could hear it unlatch and everything.
But there were bigger things too. The worst was the children's voices. I'd say on about three occasions we woke up to the sound of small children. The first time my wife thought that our son was calling her, but he was fast asleep. It was this drawn out whisper, like "Moooom... Mommyyyy..." over and over. The hairs on the back of my neck stand up just thinking about it. When we had a newborn, we heard a little girl saying "Hey, come here, come look at your baby." Sounded like it was right next to the bed.
It wasn't just children's voices though, we both woke up one night to hear two adult voices having a heated conversation right in our closet. It is impossible for a full-size adult to fit in our closet, it was tiny. My wife said something to make it stop and there was a BANG! Like something was knocked over. But like I said, nothing could really fit there, so there was nothing to knock over.
Also, the apartment next to us had some interesting tales. We had several sets of neighbors come and go over the years. In the first set, a husband and wife, the husband was driving into the parking lot after work and saw, very distinctly, an old man in a hospital gown sitting on their bed. The bedroom window was right there as you drove in. He confronted his wife about it, she didn't know anything, and it was actually a pretty big fight. They were having marriage troubles and he must have thought she was cheating on him.
A few weeks later, when she was coming home from the grocery store, she saw the exact same thing-- an old man in a hospital gown sitting on the bed.
Fast forward a few years later. Totally different set of neighbors. We were chatting with them and somehow got on the subject of this building being an old ER. One of the neighbors said "You know, we saw the weirdest thing when we pulled in the parking lot last week."
Yep, an old man in a hospital gown, sitting on the bed.
I don't consider myself superstitious but man, that place gave me the creeps.