Gotta agree with EKM. THe 30-06 is the most versatile cartridge ever developed.

That's not to say that there aren't a number of other cartridges that will also work but the 30-06 has more factory loadings available of any cartridge, it is about as inexpensive a big game cartridge there is to shoot, ammunition is available anywhere in the world, every rifle manufacturer chambers multiple rifle models for the 30-06.

All the reasons I listed above is exactly the reason I bought my son a 30-06 for his first "real" rifle. He too will need to use it for southern whitetails to big Colorado elk.