Sounds fun;
Top quality semi-auto pistol, I'd say a SIG in .357SIG
Great quality, multi purpose bolt rifle, say a Rem700 in .308 or thirty-ought.
A M1 Garand (No collection is complete without one)
A .22LR rifle for hunting, bolt or semi depending on local laws (or how much you care about them
Finally, a good quality MODERN
battle rifle. Call it a FN/FAL or a AR-10. If you ALREADY had a Garand, and the bolt gun, I suppose a .223/5.56 AR would fit in. Of course, you've already got a .22
You'll note, no shotgun. I personally have little to no use for them, I can't see them doing something that a well-aimed rifle can't do. I also don't like bruising up my shoulder on range day.
I think we'd all agree that
some quality, semi-auto pistol is a requirement, same with the .22LR rifle.
As for the bolt action thirty ought or .308... you can load it for everything from rabbits (stretching it, for sure) to moose. you could do an African hunt with a thirty-ought if you weren't interested in elephants or buffalo.
The Garand... I suppose if you wanted to get "just" a FN/FAL or similar
battle rifle, you could leave the Garand off the list. What would you replace it with, though? I guess if you had the battle rifle category covered, you could fit an AR in here somewhere. I like the simplicity of the Garand, combined with it's awesome, devastating power.
As for the battle rifle.... Nothing can take it's place. It's your own "Liberty Tooth".
YMMV, of course.