One of the movies , which I think has the best ending scene would be The Sixth Sense.

The movie starts off with a romantic scene where a guy named Dr. Malcolm who is a well known psychologist and his wife. Things turn horribly when they see a half naked man in their bathroom shivering. As the man speaks they come to know that he was an old patient and Malcolm had failed to treat his condition.Things get intense when the patient removes a revolver and points it to Malcolm. Malcolm tries to cool him down but he fails and the patients shoots his stomach just before blowing his head-off.

The next scene shows Malcolm few days after this incident where he meets a 9 year old kid as they had an appointment earlier on. According to the kid, he saw dead people all the time, and he says that the ghosts wanted him to do them some favors. Malcolm who at first didn’t believe the kid, changes his mind as the movie continues. He helps the kid to fulfill the wishes of the ghost. But since the incident, there is a distant between the husband and the wife for which the reason is unknown.

There are lot of other things that happen before the ending, but i will just jump into the it.

At the end, Malcolm sees his wife sleep-talking while on the couch saying ‘Why did you leave me, Malcolm?’. A ring falls off her hand onto the floor when he moves. Malcolm is shocked when his ring on the floor, which he usually wears. He then remembers the kid saying that he sees dead people all the time and that they don’t know they are dead. This leaves all the viewers speechless. The whole time, Malcolm was dead and he was talking to the kid not knowing he himself was a ghost.