This answer about the contents of the briefcase contains an interesting quote from Roger Avary, the co-writer of Pulp Fiction:
Originally the briefcase contained diamonds. But that just seemed too boring and predictable. So it was decided that the contents of the briefcase were never to be seen. This way each audience member would fill in the blank with their own ultimate contents. All you were supposed to know was that it was "so beautiful." No prop master can come up with something better than each individual's imagination. At least that was the original idea. Then somebody had the bright idea (which I think was a mistake) of putting an orange lightbulb in there. Suddenly what could have been anything became anything supernatural. Didn't need to push the effect. People would have debated it for years anyway, and it would have been much more subtle. I can't believe I'm actually talking about being subtle.
If the co-writer of the movie not only didn't come up with it, but thought it was a mistake, this makes me curious: Who did come up with the orange lightbulb?