For example, cookie cutters have saved many of my projects:
I buy the cookie cutter sets that come in graduated sizes.
Another favorite of mine is parchment paper. I will cut a piece that is just large enough to cover my baking tile and work the clay on it, and then pop all three in the oven. This is especially useful if you are using a very sticky clay.
My last example is toothpicks. I think I have used them for just about everything. I have used them to apply alcohol ink, shape edges, remove fuzz and widening bead holes. I usually pierce my beads with a straight pin and then gently enlarge the hole with a toothpick.