Okay, well they aren't that cool... but it does give you a sense of accomplishment knowing that you put enough miles on your feet to lose a toenail. This has happened to me a few times and I've heard it can be due to your shoes being to small making your toes jam up against the front end. There must me some truth to that because I have also poked my second toe on both feet through many pairs of socks.
I get much pleasure out of wearing sandals when I have a toenail on the brink of falling off. This always gets a good rise out of my girlfriend. She thinks it is disgusting, but the cool factor of losing a toenail due to training out-weighs the fact that she is repulsed by the sight of my feet.