Movies that are Westerns/ Another Genre

Serenity (2005) - Sci-Fi/Western.

Bone Tomahawk
A Million Ways To Die in the West
OKLAHOMA!
Wild Wild West
Cowboys vs Aliens
Jonah Hex

Maverick
Last Man Standing (western/gangster)

Carry On Cowboy
Calamity Jane
The Proposition
White Buffalo
El Mariachi trilogy
Assault On Precinct 13
Near Dark
Red Sun
Ravenous

Solo: A Star Wars Story

I really dig that movie.  Hated it the first time I saw it, really came to enjoy it the second time around.  I think it was the goofy score that put me off the first time.  I think they were going with 'playful, frantic' in some of those scenes with the villain chasing them down; which kind of makes sense considering the plot, but it would've been a completely different film with a more foreboding score or stuck with the haunting feel of a track like Boyd's journey.    

Many, many TV western episodes were western/mystery hybrids. There’s a guy named Mike Grost who has a list of them here. One of the Mavericks (“Black Fire,” if I’m remembering correctly) is a full-fledged Agatha Christie-style whodunit. And of course The Wild Wild West, which is part mystery, part western, part sci-fi, part spy show, and all wonderful ‘60s pop surrealism. I’m not exactly sure what makes mysteries and westerns so compatible—maybe the fact that many marshal characters are already detectives, or at least lawmen? And they certainly do a lot of tracking down criminals and/or suspects.

Another mystery-western suggested to me here was Five Card Stud (’68), which I haven’t yet seen. I did see yet another example, Breakheart Pass (’75), which I feel like I should have liked but which was just leadenly paced.

Oh, one more thing about movies and mysteries: Howard Hawks’s westerns rarely have much mystery in them, but they have a lot of detective work—that famous tracking to the bar scene in Rio Bravo (repeated in El Dorado and Rio Lobo) being the most noteworthy example.