[.300 Weatherby Mag]

Supposedly Ruger is chambering their No. 1 single shot in .303 British, if you want something different. You'd probably have to order it. Sooner or later they'll probably get around to .303 Savage, too, which would also be different.

http://www.ruger.com/products/no1Lig...ets/11348.html

I really doubt that you will see a number one in .303 Savage as that round never caught on and its difficult to find ammo for.. Now the No. 1 in 300 H&H.. I could adopt one of those pretty easily...