I have an inverted bleeding peace sign on my left arm (my own design) that I drew to remind me that the brief moments of peace are fleeting, and can not weather the storm of turbulance and despair.
On my back is a large detailed skull with ripped flesh and all sorts of things going on underneath. (mostly my own design, another artist friend of mine helped with the rest) That one I drew as a symbol of how I was feeling at the time. As if my true face were not my own and underneath was a torrent of things going on that I had no control of.
I have several more planned, but haven't had the chance (or money) to do it lately.