Just for the hypothetical... I'd have to go with my Mossberg M590a1 for home defense (same job it has now - 9 rounds of 00 buck will take care of just about ANY home defense problems short of an entire platoon).
For an offensive battle rifle/hunting rifle/all around rifle, I'd go for a M1 Garand that I'd "ruin" with a really nice modern optic, maybe a new barrel, and that'd be that. It'd be more accurate than I'd ever need, and I'd wager that with a Garand and 1 extra clip I'd be able to inflict about as much damage as twice that number of rounds from an AR, and from a longer distance.
The previous generation of battle rifles were called battle rifles for a reason...