The ultimate "western movie spoof" - at least in close competition with Cat Ballou, has to be The Villain." (1979?)

Kirk Douglas plays Wile E Coyote to the hilt. Arnold Swarzeneger is "Handsome Stranger" (named after his father), wears the white hat and carries a seven-shooter, and Kirk's horse is as good as - but a little different than - the similar role in Cat Ballou. (Both horses should have won the oscars.)

Ann-Margret plays Ann-Margret, but does it very well.

Little Big Man is another slightly "different" one that I don't think has been mentioned. It's one that some like and some don't, and suffers from a few "disjunctions" in plot (assuming you accept that there is one), but is worth looking up, if not watching.

John