In the BoB, I think 2 knives are required, 1 that is for serious or heavy duty use, Kabar USMC, good, Glock half serrated, and half plain edge, my choice, the cold steel 5" SRK, and the trail master. 2nd, a multi tool, like a good leatherman, especially the wave, or a Gerber, can opener, saw blade, screwdrivers, scissors, toothpick, tweezers etc... I preferr the Kershaw sharpener, modular and light, with a diamond grit blade, it works, not the the best for super fine edges, but go's to work fast, and definitely workable, weighs very little. A machete is an excellent tool, I keep one in my truck tool box, along with a cheap wood saw. Last, in my everyday pants, a Spyderco, EMT, orange handled blunt point, serrated, and a full size, 5" voyager, a lot of big knife, that is always on my person, if my pants are on of course. A p38 can opener on your key ring, is a good tool as well.