Atheist author:

Robert Heinlein

One man's theology is another man's belly laugh.

Me.

And Richard Carrier.

Mark Twain.

Man is a Religious Animal. He is the only Religious Animal. He is the only    animal that has the True Religion--several of them. He is the only animal that    loves his neighbor as himself and cuts his throat if his theology isn't straight.    He has made a graveyard of the globe in trying his honest best to smooth his    brother's path to happiness and heaven....The higher animals have no religion.    And we are told that they are going to be left out in the Hereafter. I wonder    why? It seems questionable taste.
- "The Lowest Animal"

I'm going to say Thomas Paine.

Paine was really a Deist, but he hated christianity possibly more than anyone in history.  He was also called " A filthy little atheist" by President Ted Roosevelt.  I think both points make him worthy of mention in the thread.

Also-since the Deist god just creates and then leaves forever..... one doesn't have faith in him, just that he created long ago.  He no longer exists, has no point, etc.... that's closer to atheism than theism.

Atheist:

Bertrand Russell (1872-1970).

Humanist:

'Abdu'l-Bahá aka Abbás Effendi (1844-1912).