This blackspot tuskfish, found in Australia's Great Barrier Reef, held a clam in its mouth and smashed it against a rock to reach the food inside. This photo is the first incontrovertible proof that fish are capable of tool use.
While tool use was once seen as a uniquely human behavior, decades of animal observation has proven just how wrong that really was. We've seen primates, crows, and maybe even octopuses show signs of tool use. But outside of mammals, birds, and octopuses, tool use is close to unknown. There were reports of fish tool use, but no hard evidence to back it up.