It is hard to beat the versatility of a 30-06. You can buy off the shelf ammo from 150gr all the way up to 220gr. They even make some ammo that is larger and smaller, but harder to find. I have a ruger 30-06 and love it. I bought it b/c I have been moving around the last couple of years, and with proper ammo selection and shot placement, I can take out almost anything in North America.
But as everyone else has said, deer can be killed with anything from a .243 on up to a 45/70 or some obscure mag round. If it was just going to be a white tail gun, .270 is also hard to beat. I tend to stay away from magnum rounds. Off the shelf ammo is more expensive and harder to find.
It's a fact that 70 percent of the people who purchase heavier tackle do so with the categorical I just lost a huge snook! Einstein Hairdo.The other 30 percent have either Tarpon Fever or are sporting a hand cramped into a claw from a deepwater grouper.