I have experienced many strange things, including apparitions as a tween and unexplained movements by inanimate objects as a teenager, but the following story clinches it for me when it comes to believing in "ghosts."
One of my first jobs with any real responsibility was as the cook at the first Cajun/Creole restaurant in town on Bardstown Road, Cornucopia, in the Louisville Highlands (the building is still across the road from the Taco Bell two houses up from the Highland Taproom Grill). Prior to becoming Cornucopia, it was an antique store owned by an older woman who reportedly died in her apartment above the business, and before the renaissance of dining in Louisville and "Restaurant Row" on Bardstown, many eccentric, old women ran similar stores which never quite made it.
Many odd things had already occurred prior to my experience, including utensils and pans falling from hooks in the kitchen directly behind you as you passed beneath them for no reason. There was also a female server, who was also a stripper, who claimed to have been pushed in the back as she went down the stairs by no one. Our theory concerning this was that "Matilda" (my name for the old lady) was angry at having a 'hussy' on the premises.
At the top of these stairs, which were quite steep, you turned around to enter the stockroom at the first door on the right. Further down the landing/narrow hall, was the bathroom at the end, and the office through a separate door on the right as well. The stock room and office were directly over the kitchen. The stock room connected to the office through an arched doorway which was blocked by two upright freezers, so you could see in between them into the office but you could not squeeze through.
One early afternoon, I got to the restaurant before anyone else. I was in the stockroom changing into my work clothes (Cajun is heavy on the seafood and makes everything on you smell extremely nasty) and as I was pulling on my stinky, blue work-slacks, I heard a loud, repetitive squeaking noise coming from the office. I peeked between the freezers and saw the office chair behind the desk rocking back and forth as if someone invisible was really giving it a workout. As I tried to take this in, the bare light-bulb hanging above the office desk, which was previously off, became extremely bright as if over-energized and exploded.
I made it down the (still very steep) stairs with my pants still around my ankles. My bosses, Lisa and Randell, a married couple, had arrived by this time so I pulled my pants up before they saw my underwear. Lisa asked what was wrong, that I looked really scared. I told them what happened and so Randell went up and confirmed that the bulb was still screwed into its socket, but not turned on. Still scared, I went up to see whether I was nuts and the bulb was still in one piece. As Randell unscrewed the busted bulb with a pair of pliers, I looked at the chair, which sat completely still, as it seemingly laughed in my face. At least the bulb busting had actually occurred.
I worked there for a little while longer and I never had such a similar, concrete experience. Many years later, the building had become a New Age spa, and I got up the gumption to ask them if they had ever had any strange experiences happen upstairs in the back. The woman I asked, who had been somewhat friendly up to this point, became cold and looked at me stonily as she denied anything else ever occurring.