There is no such thing. If you're in brush country, and shooting at closer (100 yards or so) ranges, a slow heavy slug like the .30-30 (it won't bounce off twigs like lighter, faster bullets will). Wide, open country and longer range, something like a .308. Maybe a 7mm Mag for mulies. I've taken more deer with a .243 than anything else.
I think it really depends on where your going to hunt and how far you can take a shot.
I use a 30-30 in california because deer are smaller. The rounds are cheaper and get the job done. I shoot a 300 win mag for deer in CO and UT. BIgger deer and they drop.
Also depending where you live ammo can be limited. So i would say 30-06. Its a big bullet to take any deer and almost every ammo shop has the ammo available.