on the movie pulp fiction what was in the brief case?

Answer 1

...rather than recycle the same answer I've used since first encountering this question (i.e., my breakdown of the suspected 'soul of Mercelis Wallace' theory), I'm inclined to say that the reason for this movie's unexplained subplot, is to garnish perpetually obvious 'water cooler' conspiracy theory talk, which has apparently sustained itself years later since the film's release.

Folks!!! This HAS to be the most, if not one of the most asked questions on Yahoo! Answers!!!

Hey, Quentin Tarantino!!! If you're intent was to perplex and manipulate your audience in this way....uh, it has worked!!!!

Answer 2

It was nothing specific. It was left to the viewers imagination as to what it is. The following is a partial transcript from an interview Tarantino had a couple of years ago:

PB: We can’t leave without asking the one question you always refuse to answer. What’s glowing inside that briefcase in “Pulp Fiction”? And for that matter, what happens when Mr. Pink runs off after the shootout in “Reservoir Dogs?”

QT: I’ll never explain what was in that briefcase – not to be a pr**k but because people come up with their own explanations, and that is the explanation. Same with Mr. Pink.

I once said this as a dig to Oliver Stone, but I don’t really mean it as a dig anymore. When Oliver Stone does his movies, he has a big idea he wants to get across, and he wants everyone to leave the theater with that idea. They can reject the idea, but they’d
better get it or he’ll think he didn’t do his job. I want to do a whole lot of work for you, but I want to leave 10, maybe even 20 percent for you to imagine so the movie is really yours. You have a version. Stuff that’s open for interpretation, I want your interpretation. The minute I tell you what I think you’ll throw away whatever you’ve come up with in your head. You can’t help it. I would too. You’d feel like a fool.

So you tell me what’s in the briefcase. If you think it’s Marsellus’s soul and he’s bought it back from the devil, which is one guess I’ve heard, you are right: It’s his soul. That I actually did a movie that can inspire such wildly imaginative readings makes me proud.

Answer 3

No one knows for sure. It was left a mystery. However alot of people think it was the boss's soul.

Answer 4

There are very good explanations here:

http://www.straightdope.com/mailbag/mpulpfiction.html

Answer 5

nobody knows