Someone's already said Mal's gun from Serenity, and Dirty Harry's Model 29. My interest in guns started with film, so... Here are several. Mind you, when I started this list, I didn't realize it was revolver-specific, but I'll try to add mostly revolvers.
Han Solo's DL-44 (Mauser)
Ash's boomstick (I own a very similar AyA)
Max's double barrel (if only it didn't take a tax stamp)
Brisco County Jr's Peacemaker (a runner up to Lord Bowler's Mare's Leg)
Which is literally the same firearm as...
And back to topic, as far as revolvers...
And Bronson's first Death Wish firearm
The FIE Titan from Dawn of the Dead (one of my favorite films, to the point that I'd consider one of those junk guns just for the nastalgia)
And Flyboy's Single Six (the majority of the firearms on that film are .22s or plastic blank-firing rifles)
Since I can't do Callahan's 29, there's this one.
And a Safety Hammerless
You'll notice Harrison Ford, Bruce Campbell, and Eastwood come up more than once in my list. Might sort of indicate who my heroes are.
And of course
Really, my favorite firearms are almost all revolvers and shotguns. I think it points back to the age of exploitation film in the 60s, 70s, and 80s, when most sets were using real firearms and autos couldn't cycle blanks, so everyone had revolvers or shotguns. They're just more tasteful to me, and I'd say that's why.