DUH, M249 SAW. If I can only buy one more gun, that means everything has turned to crap, and my guys will need an automatic for suppression.
Guess I would take a little different direction than most. If there was only one more to be had it would be an old Ithaca NID sxs shotgun. The reasoning behind that choice is that one day I will no longer be able to run the fields chasing game and will have to be content sitting in a rocker listening to the old double barrel lock up, thinking of days gone by.