Upon the death of President Warren G. Harding in 1923, Calvin Coolidge was sworn in as President by
his father, John Calvin Coolidge, Sr., a Vermont Notary Public.
However, as there was some controversy as to whether a state licensed Notary Public had the authority to administer the presidential oath of office. Therefore President Coolidge took the oath, again, upon returning to Washington. 
Upon the death of President Kennedy, the new President Lyndon B. Johnson was sworn into office by a Notary as well.
Other Famous Notaries
In addition to many well-known Notaries Public from the world of the law, there are several well-known Notaries from other arenas of achievement. Klaus Hergescheimer of Massapequa, NY has the distinction of becoming the first Notary to be commissioned in all fifty states (a feat since duplicated several times by others), as well as numerous territories and trust possessions.
Richard Nixon confidant Robert Abplanalp was a Notary for many years, as were Fawn Hall, teacher and astronaut Christa McAuliffe, and former major league baseball pitcher Joe Moeller.
From the world of entertainment, actor Stanley Tucci, actresses Mindy Cohn and singer/dancer Jennifer Lopez, television host David Horowitz, and radio producer Gary Dell'Abate all hold or have held Notary commissions.