I would vote for the C. Sharps version of the Win 1885 Hiwall, since you can customize the barrel length, caliber, and stock style for not much extra. Extra cost over a Japanese "1885" is worth it to me--I just like the company and the fact that you can go to Big Timber and see how they are made and talk to the men and women who are actually gonna make YOUR rifle. Since I don't like rimless ctgs. in a traditional single shot, their selection of calibers suits me fine. I have a .44-40 because that "pistol" caliber is acceptable on all ranges including indoor ranges in CA, and a .30-40 for hunting big stuff. (Some of my handloads for the .44-40 are NOT pistol ammunition!).
I also have 2 Ruger #1s and like them a lot. And a custom Martini Cadet in .25-35. And some "real" Winchester 1885s, a Hiwall .38-40, a re-barreled .30-40, and a Lowall .25-20.
But if I had to have ONE single shot rifle, it would be a T-C G2 Carbine, because you can "make" it into so many guns by switching barrels (and stocks if you want to). So far mine is a 17" .22WRM for varmints, a 20" .32-20 to go with my Colt "Army Special" revolver, and a .410 for cottontails and "things that go 'bump' in the night." (I'm looking for a 28 ga. shotgun barrel for it for quail hunting and skeet). It isn't traditional and it sure is ugly, but it really shoots, is very handy to carry, and is great value for the money. It WILL handle big game cartridges in a very handy package, too. I just have other guns for that.