Anything you shoot well from .243 to 30-06. With the right bullets any of them will do a fine job, if you do your bit. Let's be honest, any difference is all in our mind and the deer will not notice the difference with a well placed shot.
I currently hunt with .243, .270, 7x57, 7x64, .300 Savage, .308, multiple 30-06's, and several larger and smaller (from .223 to .458 Winchester). Sometimes I use my .300 Winny, but that's just so it doesn't feel left out, you really don't need it for deer hunting.