Limpet sea snails may be small, but their mouths pack a big punch. They have a row of tiny teeth made of the hardest biologically produced substance ever discovered. In addition to an "almost ideal" mix of proteins, the teeth are reinforced with a natural nanofiber called goethite, which contains iron.
Limpet teeth are 100 times thinner than a human hair, though, so what are they good for? The limpet attaches itself to rocks, where it feasts on lichen and algae. In addition, the teeth help the two-inch snails grasp onto rocks when the tides roll in, insuring that they aren't swept away. The teeth are so strong that they scar the rock (microscopically.)
Don't worry though, you can still eat limpets.