Rob Peterson at 2015-03-03 14:09:11:
A great one would be "Raiders of the Lost Ark" where Indy decides to go after the truck with the ark, and Sallah asks, "How?" "I don't know," Indy says, "I'm making this up as I go." Not only does it show Indy's intelligence, but it also it shows his instinct and inventiveness, including that of Harrison Ford, who changes the line "Where is it?" to "Truck? What truck?"
YouTube: https://www.youtube.com/watch?v=FVdRfnLPypE
"Raiders of the Lost Ark" dialogue/directions
-- http://www.imsdb.com/scripts/Indiana-Jones-and-the-Raiders-of-the-Lost-Ark.html
Gobler nods and runs off. Shliemann heads back toward camp.
Belloq hesitates a long moment, studying the burning wreckage
with an odd, suspicious look. Finally, he turns and leaves,
passing a nearby stack of barrels. When he has passed, Sallah
appears from among the barrels. He searches the crowd for
his people and starts a broken field run along some tents to
avoid a group of Germans and is running flat-out when someone
sticks out a leg and sends him flipping. Sallah, dust all
over his face, looks angrily toward the concealed culprit.
At once, a flashing white grin splits his darkened face.
Indy and Marion, splotched with soot and oil, are hiding in
the flap of a tent. Sallah runs into their arms and the three
embrace warmly. When they break -
SALLAH
Holy smoke, my friends! I am so
pleased you are not dead.
MARION
Us too.
SALLAH
(suddenly remembering)
The Ark! They're taking it on a truck
to Cairo.
INDY
Where is it?
Sallah gestures to follow and all three run off stealthily
through the mostly deserted camp.
EXT. AMONG THE TENTS - DAY
Sallah, Indy and Marion run into a hiding spot behind some
water barrels near the Command Tent. They peek out at this
activity -
In the big space near the Command Tent is parked an open
German staff car; inside is a Blond Driver and an Armed Guard.
Directly behind it is a canvas-topped troop truck. At this
moment, Belloq and Shliemann are supervising the careful
placement of the crated Ark in the back of the truck. When
it is securely placed inside, we hear an ominous marching
sound and Nine Armed Nazis appear at a trot from between
some tents and climb into the back of the truck with the
Ark.
Behind the water barrels, Sallah and Marion exchange hapless
looks, But Indy just concentrates on -
The scene by the truck: Belloq and Shliemann are about to
climb into the front staff car when they pause to check out
the final component of the convoy. Rolling into place behind
the truck is another open staff car. But this one is special -
mounted in the back is a big, black machine gun, manned by a
Gunner. At the wheel of the car is Gobler and next to him
sits Belzig.
Sallah and Marion look at Indy. Belloq and Shliemann climb
in the back seat of the front car and the caravan pulls out.
Indy watches it go, thinking hard.
INDY
You two get back to Cairo quick and
get us transportation to England - a
plane, a ship, anything.
MARION
What about you?
INDY
I'm going to get that truck. I'll
meet you at Omar's. Be ready for me.
Sallah nods. Marion looks at him like he's nuts. Indy jumps
up, looks around desperately.
MARION
How are you going to get that truck?
INDY
(still searching)
I don't know. I'm making this up as
I go.
He runs away between two tents.
EXT. AT THE EDGE OF THE DIGS - DAY
From among the tents, Indy suddenly bursts into view, happily
astride a magnificent white Arabian stallion. He gallops off
across the desert.