LEGO artist Nathan Sawaya had a tattoo artist mark his thumb so that it looks like a LEGO brick:

Every single day, I snap together bricks. Each day I am pressing down on the bumps of each brick to make sure there is a tight fit. And if I press real hard, the bumps leave little marks on myfingers and thumb. What better way to pay tribute to my medium of choice, then permanently inking those marks on to my thumb?

Link | Sawaya Website | Photo: Brick Artist