Another really good Lancaster western is Vengeance Valley with Robert Walker Sr. playing the villain in that one. It's definitely a sleeper. With that, my favorite Lancaster westerns are:
Gunfight At The OK Corral
The Professionals
Vera Cruz
Valdez Is Coming
Lawman
Vengeance Valley
Two of my favorite Lancaster non-westerns but with alot of action
The Crimson Pirate
The Flame And The Arrow
