Kat Ran Press has a display of stamps designed by type designers. The list includes such luminaries as Hermann Zapf, Adrian Frutiger, and Eric Gill, and even reaches back to Peter Behrens and W.A. Dwiggins.
I'm showing Julian Waters' stamp lettering here in honor of Veteran's Day. Besides being a great type designer, Julian is a brilliant calligrapher. His childhood was filled with calligraphy on his mother's side and book conservation on his father's side. Boy, do I envy him that. (He envies me my childhood piano lessons, but really, I just don't think they begin to compare.)