If you are looking for a used gun, probably the most common quality, double action .22 out there is going to be a S&W model 17. Look for a one of the later (-3) versions as I believe they are a bit easier to find. The 617's seem to be around also. I also see an occasional Colt OMT around and they are very nice shooters too.
Don't forget the Ruger Single six either, while not as accurate as my Smith or Colt, still a fun shooter and readily available.
I love shooting my .22 revolvers, cheap ammo and stellar accuracy makes for a good day at the range.
1975 Single Six