Another is The Ghost and Mrs. Muir, unfinished business again.
Movies
The Sixth Sense (http://www.imdb.com/title/tt0167404/) - same theme again - but thought provoking.
Ghostbusters - http://www.imdb.com/title/tt0087332/
[business is terrible at Ghostbusters]
Janine Melnitz: [answers the phone] Hello, Ghostbusters... Yes, of course they're serious... You do?... You have?... No kidding! Just gimme the address... Oh sure, they will be totally discreet. Thank you!
[hangs up]
Janine Melnitz: WE GOT ONE! http://www.imdb.com/title/tt0087332/quotes
THEME? badly-behaved poltergeists?
A number of movies have nailed key themes arounds Ghosts.
One theme that Ghost (http://www.imdb.com/title/tt0099653/), for instance, tackles is unfinished business (as a reason for a ghost to stay around).