I also think the 20 gauge is the most versatile caliber for deer-sized game and smaller.
Gonna have to give a +1 :thumbsup: for the 20 gauge.
The OP mentions deer and squirrels. Sure you can do that with a .45 or even a .40 (in some states) providing you head shoot the squirrels. The problem is what if the OP's friend wants to add something new to the menu?
Well rabbits are not a problem for the riflemen. So turkey...some states allow rifles in the fall, some states don't allow rifles for turkey at all. How about grouse or pheasant? What about as age set in, and the shooter simply can't make those head shots with a rifle? :wink:
A fusil, neat has always been a very popular gun, for several good reasons.
LD