Liver: the Salamander Organ

Did you know that if you cut a chunk of your liver off, it will regrow? Most people learn this in grade school, but it's easy to forget until you stop to think about how awesome it really is. Your liver will regrow itself. You can cut off up to 85% and it will still grow back. You could cut off more but you'd die of liver failure before it has a chance to regrow. Which, by the way, only takes a couple of weeks. Right now, you could cut yourself open, saw off a chunk of liver and in less than a month you'll be good as new (assuming you took care not to give yourself an infection in the process). No other body part can do that.