That might be a fun game to play, name this movie gun.
Prior to the 1990s, it would pretty much be limited to Winchester Model 1892 Lever Guns, and Colt Single Action Army revolvers.
The Hollywood studios owned large quantities of both. So in pretty much every old Oat Burner, no matter when they were set, you usually saw 1892 Winchesters and Colts.
Around that time the move studios realized they were sitting on a big pile of money with all those old guns and how much they had appreciated over the years, so they sold off most of them.
When movies like Tombstone came out in 1993 you started seeing more attention paid to old guns. Most of which were Uberti replicas, supplied by new businesses catering to supplying the movie makers with authentic looking guns of the era.
Prior to that time, if the movie makers wanted something that looked like a Henry, they would just remove the fore stock from an 1892 Winchester so it looked kind of like a Henry.
When Winchester '73 was made with James Stewart in 1950, they took a run of the mill '73 and sent it back to Winchester to dress it up to look like a 1 of 1000 '73. Even so, I remember seeing at least one 'Hollywood Henry' (an 1892 with the fore stock removed) in the shooting contest scene. And twice one of the actors claimed he was shooting a Henry when he was plainly holding a Model 1873.
When Tom Selleck made Crossfire Trail in 2001 he sent two original 1876 Centennial Winchesters to a smith to have them married together to make up one rifle.
After the 2007 version of 3:10 to Yuma came out, with one of the outlaws sporting a Schofield replica, Roy Jinks reported that lots of people wrote him about Schofields they owned that turned out not to be Schofields at all.
Merwin Hulbert
Here is a scene from Godfather II with one of the Italian actors holding a real Merwin Hulbert to his head.
Here is a closeup of young Clemenza's hand holding the same Merwin Hulbert in the scene where young Vito helps him steal a rug.
Here is a photo of Randy Quaid holding a MH in The Long Riders from 1980. These are originals because there are no replicas.
Here is a photo of Robert Ryan holding a Marlin in The Naked Spur. Ryan was a bad guy, and somehow he got the rifle away from Millard Mitchell. I would have to watch the movie again to see how he did that.
Other than these examples, mostly Winchester Model 1892 and Colt SAA is what you usually saw in a Western.