I finally tried out an idea I've been thinking about for a while. I usually carry chewing sticks, which are toothpicks saturated in essential oils, such as tea tree(which has antiseptic properties) and mint. They do an increadible job at freshening the breath without being harsh, last a surprisingly long time, and can also be used as toothpicks of course. You can find them in natural food stores and some supermarkets. I've suspected that they might burn well, so I tried lighting a few. These ones are made of birchwood.

When dry, it caught a flame immediately, and burned only slightly longer than a match. I suspect that when shaved, would make excellent tinder to catch a spark or coal. I then tried dousing one with water, and it caught a flame after a few seconds, but burned a lot longer. In a survival situation, wetting all but the tip would give you a long burning match that still catches very easily. I haven't tried soaking one in water for a long period of time, I'll test that another time.

In summary, a few chewing sticks can fit in any size PSK, and be used for effective oral hygiene and as tinder/small kindeling, and burns much longer than a match when slightly wet. Chewing them can also be a psychological aid to overcome hunger, smoking(they are often marketed as a stop smoking aid to overcome oral fixation), etc. Perhaps not essential, but tiny, cheap, multiuse items that are also useful in everday life are good things to think about.