If I had to get rid of all my guns except one, I'd keep my 300rum. 30 cal is one of the best suited cals out there, IMO. Not to say others won't work well. With a 30 cal light or heavy bullets work. I know folks who take 338's mule deer huntin which I think is a bit more than is needed.
Wildrose said it very well too.
I'd have to say that an up close shot would be devastating to a deer but at least it would be dead. Thats for sure. But it will handle deer way way out there very well also. GL and keep us informed