Of your options the Colt single action "Peacemaker" just says: "I'm in charge!" Especially if it is
ivory handled like Gen. Patton's. It is pretty hard to outgun an American with a .45 LC.
Probably worn in an ornate (I'm American!) drop loop rig as much for advertisement as for quick draw or http://en.wikipedia.org/wiki/Bridgeport_rig
Some options that you did not list include:
A custom Schofield. A handsome gun that is very fast to reload.
If your character is really trying to impress people maybe an old Colt Dragoon or even a Walker. There are even .45 "black powder magnum" conversion cartridges that would make a converted Walker the most powerful handgun of that era: http://en.wikipedia.org/wiki/.45_Black_Powder_Magnum_(.45_BPM)
A practical character would probably also carry a Derringer, Bull Dog, or other (probably double action) pocket pistol. Many revolvers had shoulder stocks available like:
I have a couple and they basically increase your effective range from feet to yards.
There are lots of other cool revolvers like the Webley, LeMat, and a number of Belgian models but they just would not be American signature pistols. I have seen more than one American living abroad who started wearing Stetsons, BIG belt buckles, and cowboy boots which they did not wear at home. My parents were great horse doctors but I got into cowboy action shooting (and dress) living in southern Germany.
There are also very American sawed off shotguns and mare's legs.