My favorite of the ones listed is the .416 Remington Magnum. I have a Winchester model 70 Safari Express chambered in it, and used it to take a Cape buffalo this past March. I did some research on various big bore dangerous game calibers, and it is my opinion that it is the best all around for the purpose. Here is a website where you can get some information as to optimal ranges for various calibers.

http://www.chuckhawks.com/game_range_caliber.htm

Be aware of the fact that when shooting such a rifle, it is going to punish you. If, like me, you are relatively insensitive to recoil, enjoy. While I may be insensitive to recoil, my .416 still gives me a bruise occasionally. It definitely is a trip to shoot, but is not what I would call a pleasure. I weigh 200 pounds, and it moves me back a step or two when I touch it off.