Ok, I guess I'll throw in my 2 cents.

If I was just going with one gun, then it would be a 12ga shotgun - pump (ie rem 870). Wide wide range of applications.

If I was just going with two guns, then the above plus a .357 revolver. An autoloader is 'sexier' but the wheel gun is much simpler, more reliable and easier to work on. If I was to be located outside the US though, I'd definitely consider something that fires 9mm.

If I was going with 3 guns, it would be the 2 above plus a .22lr rifle.

If I was going to go with 4 guns, then a center fire rifle in 5.56 or 7.62x51 (.308). I'd put this down at 4th, because I can't envision a high probability situation where I need to take out a target @250 meters. And any big game hunting can be accomplished by getting within 100 meters and using a slug from the 12 ga. Any smaller hunting can be done with trapping, or the .357 or 22 rifle.

Finally (and much much lower in priority to the above 4) would be a .22lr hand gun.