Pre-M15 Combat Masterpiece, ca. 1955, 4" bbl, with the older style postwar hammer. The small extra touches in craftsmanship, like the chamfered cylinder, makes it a beautiful piece to behold.
I'm also partial to old I-frames, old 4- and 5-screw models, fixed-sight N-frames, M66s, & M39s. I have a M28 Highway Patrolman that I like a lot. Come to think of it, just about any of them except the fairly recent S&Ws revolvers.
Steve