First off, I do believe in ghosts, so just to get that out there ...
Those who don't (like my wife) I respect and understand where you come from, but I've had a few things in my life and know of others who have, so that makes me believe
A few years ago I was doing a vacant house. 2-story, (I forget the age off hand, but def 80+yr old house), long time resident who had died, etc and this was for the purchase.
Long story short, had an eerie feeling walking through that I wasn't the only one/thing in there, although I literally was (no realtor, no assistant, etc) I stand at the bottom of the stairs and say "Make a noise" ... nothing. I wait about 7-10 seconds. Still nothing. I head to the kitchen, which is about 15 feet away and as I enter I hear a bottle FALL inside a cabinet! I run out the back door and yell a few expletives! I go back in to find the bottle (some liquor bottle) on its side but DEFINITELY NOT a usual way to "store" a liquor bottle! I took the last few notes I needed about the property and left.
I've had to do a number of other houses in that neighborhood over the years since then and each time I drive past that property, I feel an eerie feeling. Also, that same week, 2 friends of mine had strange/"unexplainable" things happen ... my grandmother always told me things happen in 3's ....