CZ-52 or Tokarev
I own two CZ-52s and they are two of the best shooting guns I have. I put a 9mm parabellum barrel in one and left the other at 7.62x25. Both will hit as good as you can shoot out to 25 yards.
I got one of the Romanian Tokarevs in 7.62x25 as well. It's also a great gun and shoots as good as you can out to 25 yards or so. It's a little more expensive though.
I have one of the Nagant revolvers too. That lame ass ammo they have for it is so expensive and fairly difficult to reload. You can't hit the broad side of a barn with one of these using the correct ammo for it. DISCLAIMER: DONOT TRY THE FOLLOWING, if you do it is at your own risk and I will not be held liable. I use .32 S&W long ammo in this little revolver and it works just fine. It is not the correct ammo for the gun so if you try it, don't blame me if you have problems. The gun shoots great out to 10 yards with the .32 S&W long. Only problem is you can't reload because it splits the end of the brass. Other than that, it works great for me. Again, it is the wrong ammo for the gun. If you try this, you take responsibility for whatever happens.
These are are all Misurp guns so don't expect nice, shiny perfect guns that look new. They all shoot great and ammo is cheap and plentiful for most of them. If I wanted the best of the 3 and wanted to spend as little as possible and have a good gun with cheap ammo, I'd go with the CZ-52.
You'll have to tear it down, clean it good and oil it good when you get it. After that just buy yourself one of them spam cans of 1200 round of 7.62x25 for about $80 at the nearest gun show and your off. That 7.62x25 cartridge kicks ass. It sounds, shoots and handles like a much bigger caliber than it is.
Good Luck,
Joe