I have to agree with BallardW-
The one I'm shooting at the time.
Any 22 is more fun than not having a 22.
I personally believe it wise for everyone to have a semi-auto .22lr and a revolver .22lr.
I know some complain about the revolver taking longer to load than a semi-auto, but that is more true about shooting 50 rounds from a SA revolver, like the Single-Six, than a DA/SA revolver, where you can do an ammo/shell dump to speed it up.
You just have to remember to factor in the time it takes to reload each magazine before you insert it in the gun. Don't count only the time to slap a mag home- but the reloading of the mag.
I can only say good things about the Nelson .22lr conversions as well- both in terms of quality and their support of the product.
I probably shoot my Ruger 22/45 the most, but the Nelson in creeping up on it.
I don't know you or your desires.
Each type of goal for the gun would lead to different recommendations.
That said, it is really hard to go wrong with the Buckmark or Ruger MK series handguns.
I will say that I have never met a Ruger MK series that didn't deserve to have it's ignition system and trigger replaced at the beginning. Maybe the MK IV is better. I don't know.
The Buckmark had me swap the trigger and do a spring modification, and now it is scary light/crisp. I won't let inexperienced shooters use it as it is now competition/hairtrigger light.
On the revolver front- if it is all-around fun, I'd go with a Ruger Single-Six Convertible. This lets you swap cylinders and switch between .22s/l/lr and .22mag. the drawback is that the bore is set for the .22mag dimensions, so it isn't as accurate as a S&W K-22 Masterpiece or Colt Officers' Model Target/Special/Match.
However, it is fun.
High Standards have been mentioned. I LIKE them- a lot. However, they are best for Standard Velocity ammo, and can require more 'tinkering' with the magazine feed lips than any other handgun I've experienced. rimfire central dot com has a subforum reserved for them. I own an example from 4 different decades, but can't recommend them to someone who just wants it to work without thought, and who wants to use Minimags all the time. It is from a different era and you have to have more awareness than, say, a Ruger.
And, they both look better and can be more accurate than the Ruger. The following are images from the web to illustrate my point. Sorry- can't resize it well.
High Standard 102 Trophy 'Space Gun':
Ruger MK II Government Target Model:
The High Standard always gets attention when I pull it out. The Ruger gets a glance and they move on.
What you buy to add really depends on your goals, and those are YOUR goals.
I will just say that I have never had a bad time with a .22lr handgun that was in good condition.