You might search a little on this site, there is a wealth of info on this subject. The calibers are endless, it's mainly personal preference. More info on what you want to do with the rifle will help.
Are you going to carry it in the field? If so what is your weight limit? Do you reload? are you going to use a brake? How long must the barrel last? Must the ammo be readily available and cheap? Are you wary of serious recoil? Lastly, how deep are your pockets?
Beware the fury of a patient man....