Mainstream Star Trek fans probably do not recognize the name of D.C. Fontana, other than to do a cursory Google search and learn that she's established herself as an author of several novels and/or teleplays for the original program as well as the subsequent animated incarnation as well as The Next Generation. While we may never know the depth of her entire contribution to Trek, let me mention a few listed from her obituary notice:
First, not only did she pen scripts and serve as the story editor for classic Star Trek, she also served as one of its producers, no small feat in an era when female contributions were somewhat frowned upon by studio executives.
Second, she's credited with largely "founding" Spock. The characters ongoing struggle with his hybrid status -- half-human, half-Vulcan -- was her creation, and she helped bring it alive visually with scripts for both the classic program and Star Trek: The Animated Series.
Lastly, she crafted scripts for not only classic Trek but also Star Trek: The Next Generation, Star Trek: Deep Space Nine, and Star Trek: New Voyages, a popular web-based incarnation exploring further missions of Kirk and company.
But her influence on televised Science Fiction doesn't start and stop with Trek alone: her IMDB.com profile shows that she wrote scripts for such other properties as The Six Million Dollar Man, Land Of The Lost, The Fantastic Journey, Logan's Run, Buck Rogers In The 25th Century, War Of The Worlds, and even Babylon 5. That is some record, my friends.
Alas, none of us lasts forever, and she's left our world for whatever lies beyond. Rest in peace, milady, and may your works forever burn brightly.