Special effect in the final scene...
In case no one spotted it, the final scene has a very clever effect with Jennifer's ghost.
It's pretty clear, upon several viewings, that the actress playing the ghost actually appears twice in the same image: once in silhouette, and then just her face superimposed over the silhouette with a very creepy lighting effect.
It's actually kind of obvious once you spot it, and when you do, you have to think "wow," because this means that the filmmakers really went out of their way to make that shot special. It is VERY effective, and I can't say I've ever seen it done elsewhere.
So if you're one of those people for whom the scene has stuck in their minds for years, now you know part of the reason for it -- it's an illusion that very subtly stands out from reality, but enough that it WOULD stay in your head.
Anyway, check it out, and play it several times. It actually helps to focus more on the silhouette than the face in order to spot the eerie discrepancy between the two images.
I for one appreciate this film that much more for it. Here it is:
http://www.youtube.com/watch?v=gKvk0Wh0YkU&t=91m54s