I'll go 223 (small game, varmint, 2 or 4 legged, availablebility, lots fit in your pocket)
Next, 35 Whelen. Large game. Suitable for anything in North America, and the ability to use pistol bullets for plinking or smaller game, etc.
Then the 458WM. Suitable for Africa (if I ever get the chance) and Big bears. And again, can utilize pistol bullets for reduced loads.
Add that 22lr and a 12g and you're good to go for just about anything from chipmunks to a C130 aircraft.
