How many formats for the ghost experience can you name?

Many years ago, when I was thinking about writing, I came up with a list of what ghosts could be.

Any additions and comments are, of course, welcome.

1. Actual deceased humans
   
2. Historical events repeating like a rerun, without interaction
   
3. Entities that are not human
   
4. Hallucinations
   
5. Creations like Tulpa, Egregore, Servitor
   
6. Living people in OOBE, AP, or unconsciously affecting things (many poltergeists)
   

I could swear I had more than that at one time, tick tock go the brain cells, while the memory oozes out your toes...

I think that ghosts are simply actual deceased humans who are stuck, unable to let go or move on.

Can't find it at the moment... but there was a case I read about an elderly man who had committed suicide with a shotgun, a gory and successful case, where the cleanup crew experienced a lot of disturbing poltergeist activity in his house. One worker saw a vision of him telling her to leave. As if he was stuck there because of the strong emotions and trauma surrounding his death.