I never play by the rules on these "just one threads" but I do like to play along.
So one of these below, all but one .357, in order of desire:
S&W 642 (.38 spl +P)
S&W M&P R8
S&W Model 28 6"
S&W 686 6", 7-rounder
Ruger GP-100 6"
S&W 686 4"
Ruger GP-100 4"
Colt Trooper 6"
You will see a dicotomy here.
My first choice is the 642 because it is small, light, pocketable, and could work in just about every situation to some extent. It fits very well into life in an urban environment where nearly all of us live.
The others are are all conspicously large and heavy...what I would call "outdoor guns". The 4" models would be usable for CC in an urban environment with the right clothes.
If I were hanging out in the deep woods or the desert I'd want one of the big ones.
That was fun.