Very interesting stuff. Although not all of these might be considered rare by some, they're certainly uncommon in the everyday lives of gun owners. I've had to burn up Google, looking up some of these.
1898 Springfield carbine in .30-40 Krag.
Ok, I have it at my home office now. It is a one liner.
49th post war K-22 made.
Century Model 100 with an octagonal barrel, made in Greenfield IN. LEJ Custom 100 made for SuperVel of Shelbyville IN for a left handed shooter. Only ones I've ever seen.