It would be my S&W Model 18 Combat Masterpiece,,,
Perfect balance and fit to my hand.
A very close second would be my S&W Model 63 with oversized grips,,,
The K-frame size grips make it fit as well as my Model 18.
Semi-auto:
My Beretta Cheetah Model 87FS,,,
It fits my hand perfectly and almost seems to aim itself.
A close second would be my CZ-75B Kadet,,,
It is a handful of rimfire pistol that shoots very well.
I have eighteen .22 handguns ranging from Taurus mouse-guns to Bersa Thunders to Beretta NEOS to Ruger Mk-III target pistols with some other Colt revolvers thrown in the mix,,,
I enjoy shooting all of them but my Model 18 and that Beretta Cheetah are and remain my personal favorites.
I have a S&W 10 shot revolver ... a model 617. I love shooting it. All I use it for is target practice. It is pretty accurate. Last time I had it at the range, I went through close to 500 rounds in a very short time. I like to load it, aim it and pull, pull, pull as rapidly as possible ... to see how close a grouping of 10 I can get at 25 - 30 yards. Yes, likely sounds dumb, but it is fun to me.
Funny story with this 22. I was at H&H last winter and had finished shooting a couple hundred rounds with this 22LR. I was getting ready to leave and realized I had my brought my S&W 460 with me to shoot a few rounds of my latest Buffalo Bore 380 grain hard cast, flat nose ammo. So, I pulled it out, loaded it and when the 1st round went off there was this blood curdling scream from the guy in the next booth to my right. That thing sounded like a fricking canon and the guy thought my 22lr had exploded. The guys in the same range with us laughed their asses off.
Taught me a lesson that when I change from a 22lr to the 460 I need to warn my neighbors .
My favorite is my GSG 1911-22. I've shot a crapload of misc ammos through it and it's ran like a champ. Put about 500 more rounds through it today at H&H. It's been a tack driver since I got it.