Some random thoughts:
I suppose the first thing you'll have to decide is pistol vs. revolver. I like both. I don't presently have a .22 revolver. I do have an old Model 41 Smith, which is an incredible tack driver. I don't own any SS versions, but if I were to buy one today, I'd likely opt for a SS version.
For a plinking gun that needs to be totally reliable but is likely to be beat around some, I'd likely go for a Ruger revolver--Ruger builds incredibly solid weapons, even if they don't quite have the jewel quality of a Smith, and they just don't fail. I have an early Security Six in .357 Mag which I got the month they became available 43 years ago--great pistol, and works better now than it did then, because the action has gotten smoother. It only shows a little bluing wear.
The Single 10 in .22 long rifle is interesting--10 shot revolver. Or the Single 9 in .22 WMR, 9 shots with a bit more punch. I kinda like the New Bearcat--smaller, lighter, easier to pack, and now with adjustable sights (that's on their website as a distributor exclusive through Lipsey's). Any semi-auto is more likely to fail than a revolver, although that's less of an issue in a plinking/varmit pistol than a self-defense arm. For any kind of shooting involving accuracy (is there any other kind?), I like adjustable sights.
Cary