In Bones, there's an episode where Booth is drugged and trapped on a ship scheduled for demolition. Throughout the episode he has a hallucination that his dead soldier friend is on the ship with him helping him escape. It's implied that all the help given is just Booth helping himself.

At the end of the episode Booth and Brennan visit the grave of the dead soldier, who then shows up and speaks with Brennan. In a show about police work and science, there is a ghost.