Why doesn't Bruce Willis's character realize he is dead?
If I remember correctly, the plot takes place several months after he is killed. Shouldn't there have been some clues during that time? They do imply that he thinks his wife isn't speaking to him because she's angry, but is it really possible that she was the only person he expected to interact with?
Additionally, it seems that all the other ghosts in the movie know they're dead. So perhaps another question would be do all ghosts in The Sixth Sense go through a "transition period" where they don't realize they're dead? At what point to they become aware of it?