I don't know why but when a shtf scenario is what I'm thinking about "The Hammer" which is just a tool is what first pops into my mind. Wrench (as in a garage wrench) is second. Rocks are third.My knife is a tool. So are my hammer, my pliers, my screwdrivers, my socket wrench, etc. However, I would not hesitate to use any of them as an improvised defensive weapon if they were all I had. (But they won't be all I have.)
(Heavy sigh) I guess I'm constitutionally unable to think of a knife as a weapon.