ORIGINAL: bigbulls

I would be perfectly happy hunting any one of the deer species we have with a .270 up to and including Alaskan moose. .270, .280, 30-06 etc... flip a coin IMHO.

But since you added things like polar bears to the list I would not hunt them with anything less than a 338 Win mag.

If I were doing what you are doing I would have a .22 center fire, either a .270 or 30-06, a 338 mag of some kind, and a big bore like a 416 or 458. Four cartridges and you could hunt anything in the world.