Well, the stated purpose is fun, so I'd suggest either a Buckmark or Ruger Mk III or 22/45. You can actually afford to shoot those things a ton. That failing, go all out and get a Colt's Single Action Army. If the budget won't support that weight, get an Uberti in one of the traditional SASS rounds. I'm considering an Evil Roy, in part because it is said (Gun Tests) to be an historically reliable reproduction of the SAA. Of course, it is Eye-talian!!
Or, on the other hand, anything in .41 Magnum.
If you aren't hell-bent on another handgun, and you don't have one, I'd suggest you get a lever action rifle. Sorry, but for fun they can't be beat, and they're damned good as serviceable weapons.