If I could only have one centerfire rifle it would most likely be the 30-06.
For the hunting I do with a centerfire rifle, the 30-06 covers it all.
While it may not be perfect for varmints and not really adequate for large dangerous game, its about as good as it gets for everything else.
I currently only have one 30-06 and its a M-1 Garand. Not a sporting rifle but it is a "hunting" (and target) rifle.