I had a lot of fun with my S&W 63. 4" bbl kinda kept it out of the "pocket" catagory, but it was a great plinker and tackle box gun.
Taurus 94 is much the same, but with 9 rd cylinder. Generally not as slick OTB as a Smith, but improves nicely with some use. Around here they can be had for 1/3 to 1/2 less money - new or used.
Want a 317 badly! Same fun with half the weight. Just can't bring myself to pony up the $s yet.
Outfit called "American Arms" (IIRC) used to make an Erma Werke-designed budget clone of the PPK in .22. Model was called RX-22 or PX-22, IIRC. I only saw a couple in actual use and only got to fire one. That one worked just dandy, and they were a lot less expensive than even a "beater" Walther. You might turn one up at a show for next-to-nothing.
A Beretta 21A used to be my "always" gun until the nifty little Keltec P-32 came along. Kinda picky about ammo, and I never did find anything that would run absolutely 100% for more than four or five mags full. Still a hoot to plink with, which I do semi-often. Just would be wary about entrusting my Personal Favorite Behind to it unless I had no other choice.
Astra, Star, and a few others also made teeny little pocket semis for a bunch of years. Almost all of the rimfire versions were .22 Short only. Most were of very nice quality and can be had in VG condition at low prices due to the chambering. If you've got some Shorts hoarded, they're a gas to play with.
The older Beretta "mid-sized" .22s like the "Jaguar", the Star "F" series, Astra Constable, etc. are still out there, but some are getting pricey due to collector interest.
Maybe not a true "pocket" gun, but the current favorite of my young nephews (and their old uncle) for a plinkfest is the Ruger Bearcat. Simple, sweet and hard to beat.