Browning HiPower
Actually, let me update this.
The Browning HiPower is my overall favorite, but broken down into size per the original question:
Full size: 1911, 5”, steel frame, .45 ACP
Medium: Browning HiPower
Small: Kahr PM9 Covert (though the S&W Shields are close).
Extra Small: Seecamp LWS-32
Revolver
Large: S&W 25-5 .45 Colt
“Large-Medium”: Ruger Blackhawk .44 Spl or S&W 69 .44 Mag
Medium: S&W 65 3” RB .357
Small: S&W 442 .38 Spl
Honorable Mention:
Ruger Single Six .32 Mag
Any High Standard .22 auto
Lightweight Commanders
.38 Super 1911s
S&W 12 (Airweight K frame .38, which they should bring back).