Ektopia recently posted about anatomical tattoos and that gave me the idea to post Scientific tattoos. Apparently, "geek" tattoos are big right now with more and more intellectuals getting some form of scientific message tattooed on their bodies. Here are a few that I found from a gallery on the Metro site:
This guy had the entire periodic table of elements emblazoned on his arm.
The formula for working out the Schwarzchild radius of a given mass (the radius at which, if the mass were compressed to fit within it, the mass couldn't be stopped from undergoing gravitational collapse). Black Holes.
Einstein's formula for the equivalence of mass and energy on one arm, Newton's Second Law of Motion on the other.
The graphical message that was engraved into plaques placed on the Pioneer 10 and Pioneer 11 space probes - universally comprehensible messages sent from humanity to any alien intelligences that might encounter the craft. 
A dromaeosaur - that's the family of dinosaurs that includes Velociraptors and Deinonychus.