ONE? Simple -
Sako
Caliber? Probably 270 but IF I planned to hunt the world over, and needed ammo in a pinch for all game all conditions, I'd have to suck it up and go w/the 1906...Springfield.
Pre-Garcia Finnbear in a McMillan stock will do....but I'd probably 'settle' for a SS/Syn Model 75/85...and would spring for an EDGE stock.
Leupold 6x in FXII or III
..but could 'settle' for a Leupy FX 4x33 or a Zeiss 4x32