There have been many famous UUs...

A more complete list of notable Unitarian Universalists can be found here.

Here are a few of the most famous UUs, past and present.
John Quincy Adams
Millard Fillmore
Benjamin Franklin
Thomas Jefferson
Thomas Paine
Paul Revere
Adlai Stevenson
Daniel Webster
Louisa May Alcott
Horation Alger
Ambrose Bierce
Ray Bradbury
Samuel Taylor Coleridge
e.e. cummings
Charles Dickens
Ralph Waldo Emerson
Nathaniel Hawthorne
Herman Melville
Paul Newman
Henry David Thoreau
Frank Lloyd Wright