One of the best one shot kill deer rifles I've own was a 243, anything bigger then 308 for Texas deer is simply unnecessary, my opinion for what it's worth. Proper shot placement is key.
Deer (Mule type) and Elk - 30.06
I have 2 of them but have always wanted a .308. My Dad bought me the first 30.06 for me 35 years ago, and I recently got his when he passed away. But having used the .308 (7.62) for 20 years in the military, I found that I truely love this round.
White Tail - 6mm (just wish they made more commercially available ammo)
Coyote (the sharp toothed deer) - 22-250
Racoon/skunk/possum (bandit/white striped/bald tailed deer) - .45
Squirrel (tree deer) - .22
Tin cans (aluminum deer) - all the above
I have not been deer hunting in a long time. But the only rifle I still have is chambered in 30-06. I sold my 30-30 a few years ago I still miss that gun more than I could ever miss a woman.
I prefer some thing small and modest on the little Texas deer. I like the .470 nitro express or the .375 H&H. If I was to go deer hunting up north I would like to have a little bigger round you know for knock down power in case of bears. Something like the .50 BMG (or as like to call it the .50 BFG) or the .500 nitro or a .600 nitro. Just the average every day elephant gun. Like I said I like the knock down power.
I have shot almost every caliber under the sun. However, my personal favorite is my .280 remington. Ballistically superior to the 30-06(inside 300yds.) with just as many bullet weights and handily outperforms a .270 at the same ranges. My favorite factory load, Winchester 139 or 140gr Ballistic silver tips. These bullets have also produced devastating results on hogs. I once shot one that 'squared up' to me head first, so I put one right through the top of its head that completely blew off its lower jaw bone and front leg at the shoulder. Also, I've never had to look more than 15yds off a trail to find the bucks I've shot, or shoot twice.