Anthony Scaramucci, White House Director of Communications: 6 days
Six days — that infamously short stint in the White House from Anthony "The Mooch" Scaramucci has been used as its own time measurement (e.g., Bill Shine lasted 246 days as White House Communications Director, an impressive 22.3 Scaramuccis).
Another casualty of the newly arrived Kelly, The Mooch has since pivoted to a converted-anti Trump media persona.
A profanity-laced tirade in an interview with The New Yorker proved to be Scaramucci's undoing, though he insisted his criticism of other members of the Trump administration was off-the-record.