For hunting North and South Amercian big game?
30-06. No doubt about it, for both continents especially.
I own many 30-06s. Love it’s great range of game taking capability.
Having said that, my 2-rifle battery for NA is my:
280 Rem: Pronghorns/Deer
35 Whelen: Elk, Moose, Bear
My 2-rifle battery for Africa is my:
9.3x62 Mauser: PG & DG
404 Jeffery: DG
If finding ammo replacement is a great concern, I also have and would take:
NA & SA: 30-06.
Africa: 375 H&H & 458 Lott.
This may be TMI with the Africa info. Sorry if it is.