My list is personal too - these are probably not the ten best or most historically important, but the handguns that have been pivotal just for me:
Ruger Bearcat - first handgun, purchased for $39.95 when I trapped my first mink when I was 15 or 16. Never could shoot the thing, but it sold me on portability and pride of ownership.
Ballester-Molina Argentine .45 - First big bore. Couldn't afford a Colt and these things were priced right. I was always sort of embarrassed by the pistol, but carried it in a Hunter holster when doing chores or walking the river. Remember Lee Loaders? I hammered a whole lot of .45 together to feed this thing.
S&W Highway Patrolman .357 - Another low cost option, though it didn't seem low cost when I was back in college. This was the finest revolver I'd owned. I carried it during my summer (and winter and spring break) job, driving a truck. It kept me from being robbed and maybe hurt once, and established my ongoing love of Smith & Wessons.
1911A1 Pistol - My service pistol in the Marine Corps. This is the one that taught me how to really shoot, with the help of some grizzled dudes in pith helmets. Always a love/hate relationship, I substituted a Commander (back when it was the original aluminum framed version) except for inspections and qualification. Overseas, my 1911A1 was used seriously twice and worked fine both times. I trust this pistol.
S&W Airweight Chiefs Special - As a counterintelligence officer in Asia I frequently carried one of these, as it's about the only thing that would actually conceal under the Class A uniform. One of my duties involved overseeing the destruction of over a hundred of these when flight crews were switched over to the 1911A1.
LaFrance Nova 6-Pac - This is a tiny 9mm, chopped and channeled from a Star BKM by the magician Tim LaFrance. He kept tight control of who he'd sell to, claiming that they only went to federal agents of one sort or another. As far as I know, it's still the smallest 9mm auto ever produced. I carried that in the States on the few times I still was in the spook business and packed it as a backup on the only hot deployment of my military career.
S&W Model 629-1 .44 Magnum - The perfect revolver. I bought one used from Hiram's Guns and Spirits and modified it, polished it, built leather for it, re-stocked it and shot countless thousands of Elmer Keith loads through it. Walk a can? No problem. Break a bottle at a hundred yards? No problem. Had to rebuild that first one, but not until I'd bought another as I couldn't stand the thought on not having one on hand at all times. I still think it's the perfect revolver.
S&W Model 351PD .22 Magnum - Pure fun! Seven fireballs in a row with CCI Maxi-Mags. Hitting anything with it is pure luck. Weighs nothing at all. This is the kind of toy CrackerJack should put in their boxes.
Kimber Ultra Carry II .45 - My current CCW pistol. Smaller and lighter than the Commander, reliable through the first four or five magazines, accurate, very nice to shoot, it fits in a Mitch Rosen Tito holster and is carried when I travel out of California. It's not perfect, but an excellent effort at mass-producing a small .45. In a Reno CCW class last week I put all 35 rounds inside (what was left of) the X-ring at 21 feet, rapid fire.
Ben Forkin Ruger .44 Special Old Model Blackhawk - I'd never owned anything like a real custom handgun before. After reading about his guns I found an old three-screw in good condition, contacted Ben and drove up to White Sulphur Springs to drop it off and meet the smith. We talked for hours, getting the details right, determining the health of the local elk, discussing how to raise daughters, determining what would be done with the old revolver. A year later I dropped in again and we talked for hours, but he hadn't touched the gun yet. Another year goes by and he emails me saying it was on the way and giving me the tracking number. It arrived, I opened the package and saw and handled a real custom revolver. Perfect fit and finish, every detail as we'd discussed. I grabbed a bag of Skeeter Skelton .44 Special loads and headed for the range. I had to learn all over again how to use a single action. But damn it shot well and made me look like I knew what I was doing. And other old codgers kept strolling over to see what that was I was shooting. I own a lot of guns, but this is by far the most expensive of the lot. And worth every penny. A real custom gun might be once in a lifetime for me, but I think everyone should treat themselves once.
-Don