The major players in 9x18 are the Polish Radom P64, Makarov PM (German, Bulgarian, Russian...), the CZ82, and the FEG PA-63. They can all be shot single action or double action and all are blowback. People on this forum are definately fans of blowback guns. Now for a little bit on each:
This gun was produced for the Czechoslovakian military. It has a twelve round double stack magazine. This gun has polygonal rifling, much like a glock. It utilizes bumps in the barrel strategically placed rather than traditional lands and grooves. This gun is also C&R elligible, which is interesting considering most of the examples floating around the United States were made in the 1980s, far newer than any other guns on the C&R list.
The PA-63 was made by FEG in Hungary. The gun holds 7 rounds in its single stack magazine. It has an aluminum frame, but its still robust because of the alloys utilized in its construction. This gun is not C&R elligible, but the two tone appearence sets it apart from the others. This gun can be rather annoying for left handed shooters because the guns usually have a bump out on the left grip that righties use as a thumb rest.
This gun was the military sidearm of much the soviet union for decades. Normal surplus makarovs have an 8 round single stack magazine, but some makarovs produced for consumers rather than militaries had a "widebody" grip to accomodate a double stack magazine. German and Russian ones command a lot of money and ones being offered currently in this country are usually of Bulgarian origin. Some of these guns are C&R elligible, depending on their vintage of manufacture and country of origin. It is widely held that the comercially-produced Russian Baikal IJ70 with its modern adjustable sights does not qualify as a C&R firearm.
Another thing worthy of mention is that all of these guns come apart in the same way. The trigger guard is bent down so that the user can pull the slide back, then tip up the rear end of it and slide it downrange, off of the barrel.