Jekyll is Hyde. Norman did it. I see dead people.
When I first read The Strange Case of Dr. Jekyll and Mr. Hyde, I already knew the twist. Since then, I've re-read it at least twice and watched several film adaptations.
When I first saw Psycho, I already knew the twist. Since then, I've watched it a few times, and I'm actually watching it right now. (Dadgummit, Arbogast, don't go up the stairs.) I asked for (and got) the DVD for my birthday.
When I first saw The Sixth Sense, I already knew the twist. I watched it to see the little tricks Shyamalan pulled to keep the twist secret. I haven't sat down and watched it since.
Another weird pattern. I enjoy each Stevenson book as its own piece of art. I enjoy each Hitchcock film as its own piece of art. But I watch each Shyamalan movie hoping to recapture the magic of The Sixth Sense.*
*For my money, The Village came closest.