With the resurgence of the not obsolete, though certainly in recent times waning, .450-400 3", .404 Jeffery, .450 Nitro, and even new chamberings of the .250 Savage (for most of those listed, thanks Ruger and Hornady) what would you like to see next?
I'm particularly intrigued by the .318 Westley Richards, actually in the process of having custom tooling made for my favourite barrel maker to do up a couple barrels therefor, but that'll be another thread. So that's my pick, the .318 with it's heavy for caliber .330" bullet is just a .338-06 with more class and history in my eyes. The #2 curiousity for me has recently become 6mm Lee Navy, might be my next oddball foray. .350 Rigby Mag would likely be my #3.
Your pick? .219 Zipper? .303 Savage? .30 Newton? .350 Rigby Mag?