While reading about Joel Abrahamsson's amazing shark catch (see here: http://www.vingle.net/posts/495091) I came across his point on Facebook about using shark skin to remove a tattoo he did not want.
Apparently, he got a tattoo of some kind of unidentifiable fish on his hand, and never wanted it. While fishing for the giant Greenland shark, he heard that old sailors would use shark skin to remove unwanted tattoos, so while he had the shark on the surface he rubbed his hand on the skin, which is very rough. It tore up his skin and he got an immediate infection from the slime, but the tattoo is gone! Well, all but the top of it.
It seems that he would prefer a scar from the scrape over the tattoo, because as he says: "Scars and memories is all we take with us to the grave:)"