Fantastic selections, fellas. I'll try to add a few not already listed:

The Professionals
Chato’s Land
Tom Horn
Lone Wolf McQuade
The White Buffalo

Sacred Ground
The Mask of Zorro
Young Guns II
Dead Man

A Man Called Horse
Return of A Man Called Horse
Triumphs of A Man Called Horse

The War Wagon
Red River
Rooster Cogburn
3 Godfathers
McLintock!
The Sons of Katie Elder
The Cowboys
The Shootist
Draw!

Angel And The Badman
Black Robe
Saddletramp (Hyapatia Lee, Nina Hartley)
Quigley Down Under
The Desperate Trail

The Silent Enemy(1931)
The Legend of Walks Far Woman
The Missing (Tommy Lee Jones)
Never Cry Wolf (not a western, but it has a frontier feel because it's set in the arctic under remote conditions)
Breakheart Pass

Comedies:
City Slickers
Paint Your Wagon
Three Amigos
Almost Heroes (Chris Farley)
Once Upon A Texas Train (Willie Nelson)