Lately, I've been carrying this Milwaukee box cutter knife that also has a bit holder so I always have a really sharp knife, a spare blade, and both a flathead and Phillips screw driver at the ready. Recently, I realized you could by ceramic utility blades! So, I ordered up a couple of these 5-packs for $10 each. Slightly pricy, but they are SUPER sharp and hold their edge so well.
The downside will be they are more birttle/fragile than a metal blade. Andy's a doubter. He says he's break them in about the first two minutes of work every day. That's probably true in his line of work. I keep a spare metal blade in the handle. We'll see how they do for my normal use.
If you want my advice on carrying knives and keeping them sharp… Carry one knife designed for emergencies or self defense. Put a really nice sharp edge on it and then DON'T use it. For all the other daily knife tasks, carry a razor knife. You can always flip the blade if it gets dull or you chip it. Many of them have a way to carry a spare blade too. This way, you don't have to re-sharpen your defensive knife all the time, and always have something for opening boxes or whatever utility task you need. Even better, the razor knives and blades are cheap!
