This is why we do what we do!
Most of us don't have the run of the mill cartridges in our possession (or would like to have), that is what sets up apart.
My 'oddballs' consist of 7x57mm, .303 P14's, .32-20, .308 Norma Magnum (just a good as the .300 Winchester if not more efficient), 9.3x64mm (obviously), .404Jeffery & .500 3" (in a Ruger No1). Not including others which I consider rum of the mill cartridges (.22LR, 12g. .223 etc)
All of which would also fall into this category as well.
Yes I would love to have a double given enough time & the ability of not getting shot by the wife!

Like Ruger did with the No1 bringing out the .303 again a few years back, this is what should happen to breathe new life into these fantastic cartridges again!
I certainly like all of the suggestions so far...especially the Martini; but as to what calibre....maybe a 450NE as I also have that calibre gap in my collection!

Who knows what I'll get next after my .410 H&R model 1915?
But one thing for sure it'll be something a bit different that's for sure!
93x64mm