Something like this looks pretty interesting...

http://www.spartangunworks.com/spr94_centerfire.htm

30-06/308/223 for deer, 12 gauge for all manner of smaller critters. If you also add a .22 pistol, such as a Ruger Mk II, you should be ready to bag almost any game that you can imagine.

Of course, these are not any good for the targets that are trying to shoot you. I guess that there is no such thing as one "super-gun" than is perfect for defensive use, as well as being able to bag ANYTHING that is edible.

But the spartan looks like one of the most versatile food-getters around.