This is a little harder than remembering the first duty pistol -
I still have an affinity for the 1st revolver I carried - a nickeled, .357 Magnum, S&W Hwy Patrolman (backed up by a S&W Model 39 9mm).
My favorite "showy" duty guns were a consecutive serial number pair of nickeled, 9mm, S&W, Model 59. I wore these as a pair for the 9 years I was on motorcycle duty. My most accurate (for me) was a 9mm, Glock 17.
As I conlude my 30th year, I am carrying a stainless, .45 Colt, S&W 625 and a .40 S&W Glock Model 22 (I believe in the superior ballistics of the .40 S&W, I just wish I could shoot it with as tight a groups as I got with the 9mm)
Not part of this topic, but related: My favorite off-duty carry pistols were a Colt New Service, in .45 Colt with the barrel cut to 3" and a .38 Spl, S&W stainless Chief's Special totally engraved. Both these have been sold long ago. My current favorites are: a .45 Colt, stainless, Ruger Vaquero, 3.5" barrel, and Birdshead grip and ( my latest) a blue & case hardened, .45 Colt, Uberti 1873 SAA, with 3" barrel./color]