Jean Harlow (born 3 March 1911)
For most of my college students, the phrase "blond bombshell" applies only to Marilyn Monroe--but long before Marilyn, there was Jean Harlow.
Although she died suddenly in 1937, just twenty-six years old, Harlow made a series of films that guarantee her onscreen immortality.
It's hard to go wrong with a Harlow film, but if you haven't seen it--or if you haven't watched it in a while--I recommend 1932's Red Dust, with Clark Gable.
For a complete list of her films, check out Jean Harlow: The Official Site, which also offers a brief biography. There are also great biographies; I recommend Darrell Rooney and Mark Vieira's Harlow in Hollywood: The Blonde Bombshell in the Glamour Capital, 1928-1937.