Why Bring it? You may as well ask, "Why buy diapers for a baby?" The pocket knife will be the most useful tool in your pack. It can cut food, fix a pack frame (with the screw driver or knife tip), Fight back if a mountain lion attacks (see "Safety"), pick a splinter out of skin, and clean between your teeth (toothpick - not blade).

What kind of knife should I get? The uses up above are for a standard Victorinox™ (a.k.a.-Swiss Army Knife™). But any knife will do if it has a (non-serrated) blade and a screw driver (flat head and Philips).