While the .308 or -06 are great options if a guy wanted to have a single rifle to cover everything, for this particular question, I'd lean toward .223.
I fail to see how the 223 con be more versatile all around performer than a 308 or, better, a 30-06.
I would not venture into bear country with a 223 or hunt elk or moose with it, heck it's even illegal on deer in some places as far as I know.