I think you can get away with 3 for just about any thing (but it would suck) for hunting.
1. Shot gun
2. a Practice/small game gun (22LR, 17HMR, 22mag)
3. Big game rifle (30-06, 7mm, 45/70,)
add in a hand gun (9mm, 45ACP, 357 magnum) for self defense and you have all the gun basics covered with 4 guns.
I cant think of any animal this side of the pond that at least one of these guns would not work well for.
variety is the spice of life!
Always looking for a good hunt!