I second the nomination of Sheriff of Bullet Valley. It’s a hilarious, involving, and dramatic story which is at once an energetic satire of Western cliches and a validation of the heroic ideal at the heart of the best Westerns. I also have a lot of appreciation for Gottfredson’s various 1930s Western continuities in the Mickey Mouse strip; “Lair of Wolf Barker” and “Sheriff of Nugget Gulch” are both a bit loosely structured, but have some great comedy and action; “The Bat Bandit of Inferno Gulch” is a gripping and well-plotted mystery-Western, and “Bar-None Ranch” is a great parodic Western; its satire of the gaudiest of the late-1930s/early-1940s B-westerns and its mix of Western derring-do with science-fiction gimmickry gives it a strong resemblance to “Sheriff of Bullet Valley,” and I wouldn’t be surprised if Barks wasn’t influenced by it when he created that story. I’m not sure if I would count Gottfredson’s “Race for Riches” as a full-fledged Western story, since only part of it takes place out West, but if it counts, it’s a great story, one of the all-time best Mickey continuities. Similarly, I tend to think of Barks’ “In Old California” as more of a historical adventure than a “Western” in the movie-inspired shoot-em-up sense, but if it’s considered a Western, it should also be on the short list of best Disney westerns; it’s one of Barks’ most emotionally elegiac stories, and the ending never fails to get me choked up.
I will try to list the most noteworthy ones (including ones already mentioned above):
BARKS: - Sheriff of Bullet Valley - Donald Duck in Old California!
ROSA: most chapters of the Life of $crooe are Westerns to one degree or another, but these are the more explicitly Western comics by Rosa: - The Buckaroo of the Badlands - The Raider of the Copper Hill - The Terror of the Transvaal - The Vigilante of Pizen Bluff
GOTTFREDSON: - Mickey Mouse in Death Valley - The Bat Bandit of Inferno Gulch - The Bar-none Ranch - The Lair of Wolf Barker - Sheriff of Nugget Gulch