That is a lot of poundage (I hope you were exagerating). But a knife is a necessity, I can't imagine you were implying otherwise. I never leave my house without a knife, let alone in a survival situation. As far as firearms, you don't need anywhere near 20 lbs. A firearm can serve multiple uses - food procurement, self defense, and signalling. So depending on your situation/location, that may be worth the 3-3/4 lbs of a single-shot .22 breakdown rifle and ammo. I don't have a rifle in my backpack BOB, nor do I EDC one, but I do have one in my car kit. And I do EDC a knife (a medium folder), have another one in my BOB (a medium fixed blade), and yet another in my car kit (a larger fixed blade). I do not consider any of that "wasted weight". But my kits are full of lots of other stuff too. For example, I would not leave out water and water purification methods, nor fire starting nor signalling methods, to add an extra box of ammo, etc. You need a balance of what is appropriate for your individual situation/location.