It's so hard to choose. Josey Wales, Shane, The Shootist, True Grit, the list goes on and on. I did like the lines in Shane though....
Alan Ladd as "Shane"...."So you're Jack Wilson".
Jack Palance as "Curly"...."What's that mean to you Shane".
Shane...."I've heard about you".
Curly...."What have you heard Shane?"
Shane...."I've heard that you're a low down yankee liar".
(Pregnant pause and big smile on Curley), Curley "Prove it" ....bang! bang! bang! bang! As Curley flies backward while he shoots and misses and the old man next to Shane tries to shoot Shane and Shane shoots him and then about 15 seconds later the guy upstairs shoots and wounds Shane but Shane also shoots him. I always wondered if after Shane rode off if he died or not. No way to tell in the movie and I didn't read the book.
One of my favorite scenes and a true classic. Check out that scene below if you've never seen it.....
I also loved the way Burt Lancaster smiled and twirled his revolver back into his holster after he fired, not yet realizing he had been shot by Gary Cooper in "Vera Cruz". Another classic. See that scene here....
Another one of my favorite western shootouts is "The Magnificent Seven". I liked the "lost his nerve but got it back" gunfighter character Robert Vaughn played. That last shootout was a long one where most of them all died except for Yul Brenner and Charles Bronson.
I also like the big showdown in "Wagon's East" where the supposedly meek gay guy was actually a very accomplished gunslinger and no one knew. "Oh Butch get over yourself" he said Lol, cracked me up. And the things he said when he shot the surprised bad guy who was so surprised along with everyone else at the meek gay guy who throughout the movie no one knew could even handle a gun. Not my favorite but a good one. Certainly cracked me up and probably ranks as the most humorous western shootout I've seen.
Sorry, it is impossible for me to choose the one I like best. So many are excellent for different reasons. Maybe the dialogue is great in one. The gunplay is better in another. One is longer than another. One has better acting or a character dies unusually like in "Vera Cruz". It's like putting a whole line of beautiful blonde women perfect in every way in front of a guy and asking him to choose his favorite. His only logical response would be...."All of them!"