http://www.godamongdirectors.com/scripts/princess.shtml
MAN IN BLACK What you do not smell is called iocane powder. It is odorless, tasteless, dissolves instantly in liquid, and is among the more deadlier poisons known to man.
VIZZINI Hmm.
VIZZINI, watching excitedly as the Man In Black takes the goblets, turns his back. A moment later, he turns again, faces Vizzini, drops the iocane packet. It is now empty.
The Man In Black rotates the goblets in a little shell game maneuver then puts one glass in front of Vizzini, the other in front of himself.
MAN IN BLACK All right: where is the poison? The battle of wits has begun. It ends when you decide and we both drink, and find out who is right and who is dead.
VIZZINI But it's so simple. All I have to do is divine from what I know of you. Are you the sort of man who would put the poison into his own goblet, or his enemy's?
He studies the Man In Black now.
VIZZINI Now, a clever man would put the poison into his own goblet, because he would know that only a great fool would reach for what he was given. I'm not a great fool, so I can clearly not choose the wine in front of you. But you must have known I was not a great fool; you would have counted on it, so I can clearly not choose the wine in front of me.
MAN IN BLACK (And now there's a trace of nervousness beginning)
You've made your decision then7
VIZZINI Not remotely. Because iocane comes from Australia, as everyone knows. And Australia is entirely peopled with criminals. And criminals are used to having people not trust them, as you are not trusted by me. So I can clearly not choose the wine in front of you.
MAN IN BLACK Truly, you have a dizzying intellect.
VIZZINI Wait till I get going! Where was I?
MAN IN BLACK Australia.
VIZZINI Yes -- Australia, and you must have suspected I would have known the powder's origin, so I can clearly not choose the wine in front of me.
MAN IN BLACK (very nervous) You're just stalling now.
VIZZINI (cackling) You'd like to think that, wouldn't you?
(stares at the Man in Black)
You've beaten my giant, which means you're exceptionally strong. So, you could have put the poison in your own goblet, trusting on your strength to save you. So I can clearly not choose the wine in front of you. But, you've also bested my Spaniard which means you must have studied. And in studying, you must have learned that man is mortal so you would have put the poison as far from yourself as possible, so I can clearly not choose the wine in front of me.
As Vizzini's pleasure has been growing throughout, the Man In Black's has been fast disappearing.
MAN IN BLACK You're trying to trick me into giving away something -- it won't work --
VIZZINI (triumphant) It has worked -- you've given everything away -- I know where the poison is.
MAN IN BLACK (fool's courage) Then make your choice.
VIZZINI I will. And I choose --
And suddenly he stops, points at something behind the Man In Black.
VIZZINI -- what in the world can that be?
CUT TO:
THE MAN IN BLACK,
turning around, looking.
MAN IN BLACK What? Where? I don't see anything.
CUT TO:
VIZZINI, busily switching the goblets while the Man In Black has his head turned.
VIZZINI Oh, well, I-I could have sworn I saw something. No matter.
The Man In Black turns to face him again. Vizzini starts to laugh.
MAN IN BLACK What's so funny?
VIZZINI I'll tell you in a minute. First, let's drink -- me from my glass, and you from yours.
And he picks up his goblet. The Man In Black picks up the one in front of him. As they both start to drink, Vizzini hesitates a moment.
Then, allowing the Man In Black to drink first, he swallows his wine.
MAN IN BLACK You guessed wrong.
VIZZINI (roaring with laughter) You only think I guessed wrong --
(louder now)
-- that's what's so funny! I switched glasses when your back was turned. You fool.
CUT TO:
THE MAN IN BLACK. There's nothing he can say. He just sits there.
CUT TO:
VIZZINI, watching him.
VIZZINI You fell victim to one of the classic blunders. The most famous is "Never get involved in a land war in Asia." But only slightly less well known is this: "Never go in against a Sicilian when death is on the line."
He laughs and roars and cackles and whoops and is in all ways quite cheery until he falls over dead.
CUT TO:
THE MAN IN BLACK,
stepping past the corpse, taking the blindfold and bindings off Buttercup, who notices Vizzini lying dead.
The Man In Black pulls her to her feet.
BUTTERCUP Who are you?
MAN IN BLACK I am no one to be trifled with, that is all you ever need know.
He starts to lead her off the mountain path into untraveled terrain.
BUTTERCUP (a final glance back toward Vizzini) To think -- all that time it was your cup that was poisoned.
MAN IN BLACK They were both poisoned. I spent the last few years building up an immunity to iocane powder.
And with that, he takes off, dragging her behind him.
Sorry, but that's one of my favorite scenes of all time.