OK - this is indeed a movie post.

IMDB does not sort movies by the guns that starred in it (the bastards), so I am calling on the arcommers of the world.

Help me out with a list of the movies that prominently featured this all time classic weapon.  

I will start with two I remember off the top of my head.  I am sure there are others.

1)  The Outlaw Josey Wales

2)  Lonesome Dove

It's mentioned by name in Unforgiven when Little Bill describes one blowing up in a guy's hand, "which was a failing common to that model."

Damn...good question. I doubt half of Arfcommers even know what an 1847 Walker even looks like, though.

To answer your question, however: As stated above, Unforgiven is the only one I can think of.

Slightly off topic but I've included some movies featuring Colt Dragoons also since they're basically an 'improved' Walker.
Three Amigos!  has one IIRC.  When Ned Nederlander (Martin Short) is going to have a quickdraw showdown with the German one of El Guapo's henchman make Ned switch his sissy little Colt SAA for a "man's gun" Walker he can barely hold up.  I could be wrong though, it might have been a Colt Dragoon instead.....still a heavy hand-howitzer but not quite as huge as a Walker.

True Grit had Mattie Ross carrying her dad's Dragoon.  
Rooster Cogburn: Why, by God, girl, that's a Colt's Dragoon! You're no bigger than a corn nubbin, what're you doing with all this pistol?
Mattie Ross: It belonged to my father, he carried it bravely in the war, and I intend to kill Tom Chaney with it if the law fails to do so.
Rooster Cogburn: Well, this'll sure get the job done if you can find a fence post to rest it on while you take aim.


North And South (miniseries) had some Walkers used by Patrick Swayze & others in the Mexican_American war part.

The Long Riders  Keith Carradine as Jim Younger uses a Dragoon to blast some Pinkerton JBTs who killed his (uninvolved in the gang) little brother.  

True Grit. Isn't a Walker what little Mattie was packing when she went to get her dad's stuff? Dang it! RiffRandall beat me by a couple minutes. And with a quote to boot.

The Cowboys. One of the kids showed up at the ranch with one. It was as big as he was.