My choices would be..

1) The .450 Nitro. Bullets from 300-500 grain will cover most game on earth within 0-150 yards.
2) ...9,3x74
3) ...7x65 RWS
4) ... 470 nitro
5) ... 8x57 JRS

Factory ammunition can be had easely which for me is a must. Guns can be made light without a brisk recoil.