Here is my favorite Ultralight backpacking knife. This is the only knife I took to greenland and it worked great! Cut moleskin, gutted fish, cut cord, cut more moleskin, sliced some pepperoni, cut some more moleskin.
It weighs 7 grams and the plastic part folds out to form a handle. The tip pokes out a little making the point much more useful than a razor blade. Razor blades are cool, but I don't really trust them to not slice my hand open in the dark. I have played around with a bunch of options for the cover, but haven't found the perfect one yet.
Best part? It cost me less than 2 dollars. I bought 5 of them to keep in various packs.
Did I mention it is good at cutting moleskin?