Pegs. As in clothes-pegs. Besides for hanging up clothes, we use dozens of them every week.
We have a rule here at home, that anyone who doesn't want a little thingamajig thrown away can protect it from any other person cleaning up by marking it with a peg. That can include that small nut-and-bolt-that-you-know-what-it's-for, receipts, a link of a watch strap, the half-corroded rubber plumbing washer which will serve as the sample next time you go to the hardware store, a random tiny piece of lego, a scribbled sketch of a diy project, the button that belongs to a specific shirt and is waiting to be sewed on. From time to time, we go through the pegs and see if we can actually get the thing done, instead of just looking after the little item.
Besides marking territory in that way, to keep littles safe, pegs can be used for many applications where you might need another pair of hands or some pliers - except, of course, for those needing force. Pegs are excellent to hold up a flap while you're glueing underneath, and projects involving children being creative with glue can work much better with pegs. They're great for for holding fabric or plastic in position while you cut it, or for propping something open while the inside needs to dry out. A half a wooden peg can also serve as a small wedge, and glueing them together gives you wedges of many sizes. Pegs can be used as brakes for preventing small items sliding further back on a shelf. Pegs are great for demarkating things, e.g. labling something in the fridge: Do not use this because it is an ingredient for tomorrow's pudding. We also use pegs to keep some food packaging closed: twist and peg keeps insects out. They're also great for sorting papers, at least for provisional bundles a bit larger than a paper-clip could cope with, before you've decided where to file them, and quite nice as a stand for a photo or a business-card. And recently someone here made a quick temporary mini magnet-board with a metal strip and two pegs as stands.
