3" Model 65
Having used and carried J, K and D frame .38s, in my opinion, the 3" K frame represents the optimum carry and SD wheel gun. Hits a bit harder and it's easier to hit with than a 2", yet conceals virtually as easily.
I bought my 3" Model 65, RB directly from the S&W Academy while a student there. I took more than a half dozen of them, flagged by armorers for minor adjustment, into the range, shot each until I found one that shot exactly to the sights. That was about 30 years ago and I'll never part with it.
I believe the Federal Bureau of Intimidation deserves the credit for popularizing the 3" K frame as S&W made it for them and they were perhaps the first agency to adopt the 3" K as a duty weapon. However, the wholesale transition to autoloaders was just around the corner so the 3" K frame did not enjoy a long run with the FBI.