That's a very hard question for me to answer without me pulling a Bubba C and asking what the definition of "is" is. There are so many different models and aspects to that question that it is impossible to pick just one.

I'd also have to admit that my absolute favorite S&W pistol of all is not yet in the collection. How embarrassing is that!

That said...

My sentimental favorite will always be Dad's early vintage Model 41.

The 3rd Gen I'd be least likely to ever sell is my Model 4516-1.

My favorite 3rd Gen for range use is my Model 4506 (No Dash).

My favorite for cool factor is my pre-rail Model 4013TSW

My favorite for clean looks alone is my Model 908S.

My favorite for home defense is my Model 915.

My favorite for carry is still my ratty old "used & abused" CS40.

My favorite for optimum size & fit vs. capacity is a 6906.

My favorite truck gun is... Oh wait! I don't have a truck gun!

But I still own more Model 3913's than anything else so maybe that's my real favorite?

And on and on and on...

And if we get into "honorable mentions" I'll be here all day!