Y'all are probably getting tired of seeing this one, but my keeper is my "Skeeterized" 29-3. There have been times this has been the ONLY gun in my collection.
A very difficult choice because I have four "favorite revolvers", a 617 4", a 686 6" a 27-3 4" and a 66 no-dash 4". If really pushed, I'd have to pick the 66. It has a super trigger, is extremely accurate, and I love the way it points.
I have 24 different Smith & wesson revolvers purchased very carefully over the last 35 years that fill the bill on any given day and mood. That in a nut shell is the magic of the Smith & Wesson revolver.
There is no reason I can think of to have only one gun...but to play along. I would have to say that my 629 with a 2 1/2 would fit the bill nicely. It is a blast to shoot with either my light handloads or the full on .44 mag rounds. Switch to some rubber hogues for a day of plinking then add the wooden boot grips for daily carry.
The one I would choose would be a Model 581, no dash, with a Wolff spring kit, hammer spur trimmed down to about the same size as a Model 547, and the grip frame cut down to a round butt with factory finger groove combat grips. Oh wait...what am I thinking? That's the one I already have...and I love it!!!!