Kendra tells me that a piece of graffiti found on a wall in Pompeii translates to “Everybody writes on walls except me.”
Which led me to search for other ancient graffiti. It looks like a lot of Pompeii's graffiti was pornographic and/or scatological; a fascinating look at ancient life. See also more Pompeii graffiti and even more Pompeii graffiti.
My other favorite, besides the one Kendra quoted, is this:
O walls, you have held up so much tedious graffiti that I am amazed that you have not already collapsed in ruin.
Also of possible interest: graffiti at Maes Howe, a chambered tomb in Scotland. “These runes were carved by the man most skilled in runes in the western ocean. . . .”