RE: 3 rifles for all North American game
These games are fun. I love the .243 for deer, with premium bullets. I'm not a big fan of having my shoulder rearranged every time I pull the trigger, so I'd top out at a .300 Win Mag, then either slot in a .270/.308/7mm-08 in between, or drop down to a .223 for little stuff.
My personal battery:
1) All-around/long range -.270 Win.Ruger M77
2) For bad people- 7.62x39 Russian Ruger Mini
3) Stillhuntingspecial - still working on this one, either .35 Rem. Marlin336 or .308 Win. Remington 750 carbine.