What kind of camera should be used for ghost hunting?

All you have to do is leave the camera on until you see something drift around. To add to this: the easiest way is with a double exposure. Place your camera (one capable of making double exposures) on a secure tripod and place a friend in a chair. Take a meter reading, then stop down one stop below the correct exposure. Take the photo. Have your friend leave. Re-shoot the empty chair at the same exposure. (You can take these in either order; it doesn't matter). The resulting ghost-like image of your friend will be a fake, but so are all photographs of ghosts, by definition. It is impossible to take a verifiably genuine photograph of a ghost because it is too easy to take ungenuine ghosts.