I'm going to go against the grain, I guess. I personally would recommend buying a decent utility knife. You can buy them $10 or so. A pack of blades costs a few bucks. You can replace the blade whenever it gets dull. And utility knives are designed with a short sharp blade at a good angle for cutting boxes. I bought a Stanley utility knife while I was working at McDonalds after using a Swiss Army knife and a box cutter (cheap little things that look like a stick of gum). I used my utility knife to death and have since bought another one. I think they are the cat's meow for cutting down boxes.
I prefer the all-metal yellow Stanley knives with the rubber inserts and NOTHING else. No auto open, auto close, quick change blades or any of that other crap. You can get on for $10 easy, like I said. If you are forgetful, a cheap utility knife can be had for the same price as one of those folders. Having used a number of knives one boxes I wouldn't get rid of my utility knife for the world.
