OK, so things have gone amiss but you and your loved ones are good. Your trusty M4, AK, Glock or 12 gauge is holding up fine, but is it?
What parts would you have for each? There are "spare parts" kits and such but what really breaks or needs replacing from the real world?
On my trusty old Mossberg 500A, the safety is plastic and broke in half. Not that I use the safety, but I do check it time to time.