I recently watched Flags of Our Fathers (2006) and Letters from Iwo Jima (2006) and am looking forward to seeing Gran Torino (2008) which has gotten me into a Clint Eastwood kick where I'm going back and watching his old Westerns. I also watched Appaloosa (2008) and Maverick (1994) recently, putting me further into the Old West mood.
By the time I reached Il buono, il brutto, il cattivo./The Good, the Bad and the Ugly (1966) I got to thinking about the different revolves and repeating rifles reappearing in just about every Western movie out there. Obviously there have been a great number of models with variations in styles, releases, and available calibers but below is a more simplified list covering pretty muc all of the major models seen.
It seems that the revolvers, and 'Old West' movies appear to be split up into three eras:
Often the wrong firearms are used for the period the film takes place, or percussion cap/ball-and-cap revolvers (all those prior to the 1870's) always seem to have the Richards-Mason metal cartridge conversion (Charles B. Richards & William Mason of Colt). Partly because they don't want to have the characters fumbling around with the percussion caps, because most people are only familiar with the cartridge loaded Colt Single Action Army .45 of 1873), and partly because using blanks on a film set is much saver with cartridge loaded firearms.
From this review you can see the major models by year. Images from the Internet Movie Firearms Database http://www.imfdb.org/, two images are flipped so they're all facing the same way, sacrificing accuracy for easier comparison.
Revolvers:














