While snorkeling in Palau, I saw a tuskfish using a rock as an anvil. This had been observed on a yellowhead wrasse a long time ago by Jim Coyer while we were doing a saturation dive in the Aquarius habitat off Key Largo. More recently a tuskfish was observed in Australia doing the same thing. In Palau I was able to take a video of the action, and published it here.
Below are some links to the story and the original video