My best ever...was played with for many years but I treated it with respect. And my beauty makes most modern progressives mad. This antique is still played with by young-ins today. The perfect gun bring power to a society. It trains those who follow. Most think the best is their pet gun. I content most will missed the boat on the one. They best gun preserves freedom not promotes a narcissistic love affair with caliber or a designer. The flintlock gave me freedom...
If it is as in the OP, about Reliability, Accuracy, I have One in mind.
If I add Longevity of Production, Battle Proven, still used by Government Military Forces, and Police Forces through out the would.
Then, I can go on to include the availability of Inexpensive Ammo and a standard 13-1 Round Capacity there is no doubt in my mind.
The Browning Hi-Power / P-35.
The 1911-A1 is a Great Pistol, but the Hi-Power out-guns it on capacity 13-1 to 7-1 alone.
The .45 is considered a knock-down Round but the 9mm has greater velocity.
Most of the Ammo I want in .45 is sold out when I want to buy.
I can get my fave 9mm Ammo when ever I want.
Without ammunition my guns are merely finely machined, well oiled clubs.