RE: in your opinion, the best deer hunting caliber...
The best deer hunting caliber is the one that you are most accurate and comfortable with from any position. That being said, if you could only have one gun, 30-06 Springfield, If your like most of us on this board you can never have enough guns. Currently my favorite is a Remington 700 ADL in 257 Roberts, or Sporterized Swedish Mauser. Both are under 1" accurate, mild recoil and have some pretty impressive results on deer.