ghosts haunting stuff in nightmare 3 was cool, but limited. there should be much more they can do and it shouldn't all be necessarily hostile.
examples i can think of immediately:
standing in a big enough section of dirt and marking their location, adding it as an available spawnpoint for a skeleton or zombie to rise from (they can't use any such spawnpoint that they have created themselves)
blessing a living person for bullets to pass through and miss them completely for a brief period the next time they're shot at, like that one part in pulp fiction
ghosts haunting stuff in nightmare 3 was cool, but limited. there should be much more they can do and it shouldn't all be necessarily hostile.
examples i can think of immediately: