evil tendencies said:
Let's say that a very skilled shooter was going to carry a concealed .22 pistol for personal defense...what kind would he use?
There's no one answer to that unfortunately, since people have different tastes and biases (see cassar's reply) when it comes to guns, just like with everything else.
Presume this is concealed about his person? If so, tucked into pocket or waistband or in a holster of some kind? If it's a holster, belt or under the arm? Decide if the character would train to be ambidextrous so he'd want a holster positioned for
If you want to break it down in terms of your protagonist's character:
revolvers are completely reliable, but smaller capacity;
semi-autos (what people too often refer to as autos today) have higher capacity but might jam due to their mechanical complexity;
longer barrel = higher muzzle velocity, so within reason a longer-barrelled handgun could be preferable to a short-barrelled one in a smaller calibre like .22 LR, assuming the barrel (and any foresight) doesn't pose a problem with quick draw;
being ready to fire instantly is the revolver's traditional key advantage, but many modern semi-autos have multiple safeties, meaning they are now safe to carry with a round chambered;
possible brand preference;
last but not least, country of manufacture might be a factor - a European (or at least non-American) might have no desire to carry around a US piece, while the same could be true in reverse for an American shooter.
Since you just say .22, that's actually not one calibre. While .22 Short and .22 Long are now obsolete, .22 LR is the norm, there's also .22 Magnum. Any revolver chambered for the magnum version could theoretically fire LR as well (just like .357 Magnums can fire .38 Special and .38).
So, choices:
older S&W revolvers, J frame, with a shrouded hammer
S&W 317 revolver, 8-shot cylinder
S&W 617 revolver, 10-shot, stainless steel
Ruger Mark II (older) or Mark III semi-auto, available in a variety of finishes and barrel lengths
Ruger 22/45, with Bull barrel or Slab-Side
Taurus (Brazilian firm) model 941 revolver
Taurus PT-22 semi-auto pistol, rosewood grips, blue or nickel finish
Baretta model 71 semi-auto pistol (older, all-metal gun, used my Mossad)
Baretta model 87 semi-auto pistol Cheetah (modern version of above, all metal)
Baretta U22 neos semi-auto pistol (modern, futuristic looking, polymer frame)
Walther P22, polymer frame and metal slide in various colour combos
SIG Sauer Mosquito, polymer frame and accessory rail, metal slide in various finishes
Einion