wholely agree with Suzanne, but would add that personally i would stay away from hard serifs... worry more about the kerning than the letter shapes! *G*

Perhaps something designend for newsprint because those fonts are made for poor printing situations and are still easy to read after much abuse. Since your skin will stretch and discolor with age and sunshine the text will benefit from being "set" in a flexible font.

Times Europa, Zapf's Melior, LinoLetter, Olympian, Excelsior, Corona (though I don't like its kerning), the unfortunately named Nimrod, . These are all 20th century newspaper types with wide, open counters and good resilience in bad printing situations. They have the advantage of also being very closely tracked, so you can "set" the text in a somewhat larger size for the same space.

You might also go with something a bit more calligraphic. I don't think any self-respecting typographer would ever criticize you if you chose Palatino. Adobe's Brioso and San Vito have a bit more of a hand-lettered look but still retain excellent legibility.

Although it would give the text a quaint, nostalgic flavor, I would recommend against any sort of didone type like Scotch Roman or Bodoni. The hairline serifs would fade or distort far more easily.

BTW, before you have the tattoo done, make sure your tattoo artist does a practice run on something other than your skin, like a piece of very soft leather or something. You want to make sure he can get the rhythm and tracking right before he starts sticking you with it.