Military & Police/Model 10 and its variants. It was the only one made by S&W during WWII, all others were ceased in production if I'm not mistaken, at least regular full production, and it was the first one made available for civilian sale after the war. Its been in constant production since 1899, correct? No other S&W revolver can claim that, none. It may not have the "aura" around it like some of the others mentioned but its been the mainstay all these years. These days I do believe the 642 currently holds the number one sales record. I've heard that mentioned in numerous places including from Smith sales reps.