Knight just went out of business.
There is no reason for a short magnum in a single shot.
The Ruger #1 is arguably one of the greatest rifles of all time, single shot or otherwise. I currently own four; one a custom varmint rig with a 28" Lilja stainless barrel in .220 Swift, a 1A Light Sporter in .30-'06, and two Tropicals, one in .375 H&H and the other in .458 Winchester Magnum. They are all fantastic hunting rifles in their various niches.
Other choices are the Browning High Wall or Low wall, the Blaser, the T/C Encore, and the H&R Handi Rifle. The Browning is a beautiful rifle, and is available in a good variety of calibers. It's about the same price as the Ruger. The Blaser is very expensive and kind of quirky, but a very good rifle. The Encore is typical T/C - function wins over form; ugly but hell for stout, accurate, and it has interchangeable barrels, including a muzzle loader barrel. The H&R is cheap and ugly, but very accurate and strong. It, too, can have interchangeable barrels, but you have to send it to H&R to get new ones fitted. I think it still has a muzzle loader barrels as well.
Then there are the semi-custom recreations of 19th century single shots, like the Shilo or C. Sharps Arms '74 Sharps, the Ballard, various Highwalls from Ballard, Meacham, C. Sharps, and others. Most come in at least one or two calibers that can be used with modern ammunition so you wouldn't have to reload for them. .45-70, .38-55, .32-40, and others still have ammo available.
For a first single shot, I would recommend the Ruger. They are pretty scarce at the dealers right now, so you might have to check the shows or on line. And what could possibly be better looking than a Ruger #1?
