Use: Cleaning up oil spills and softening bread
One good thing to come out of the Exxon Valdez catastrophe in 1989 was that a stylist thought of a way to repurpose all that hair that gets swept up from the barber shop floor. Hair attracts oil, whether on your skin or in the ocean. Unlike spongy material that expands when it soaks up oil, hair attracts oil only to its surface. Stuff a bunch of human hair into regular old stockings and you've got an incredibly cheap and effective, albeit gross, oil-boom system.
L-cysteine, an amino acid synthesized from human hair (or, less frequently, duck feathers or pig bristles), is used to keep bread softer for longer periods of time. Unless you only buy small-batch bread from local bakeries, you've almost certainly eaten it.
Related: The Biggest Hair Myths You Should Get Out of Your Head