A durable baked good is the bagel.  Thousands of years of proven performance.  I'm talking about real bagels, not the WonderBread-itized bagels which dominate the supermarket shelves.  I find the cheapest generic/store brand bagels are the most durable you can get at the supermarket.  (If you're lucky enough to be near a kosher bakery, get your bagels there.)

It is the only bread I do not have to worry about its location in the food pack.  Practically indestructible, maintains its integrity after numerous crush cycles, versatile enough for every meal, comes in plain and flavored.  Nothing comes close, IMO.