I have taken (leftist) libertarian lessons from a number of prominent novelists and essayists. Some are pretty strongly left-libertarian (Thoreau and Paine) while others are classical liberals, or mid 20th century anti-authoritarians.:

1. Thoreau: For Civil Disobedience and Walden
2. Huxley: For "Brave New World", depicting a soft-totalitarian state...and for coining the term "Herd Poison" in "Brave New World Revisited".
3. Orwell: for 1984 and his essays.
4. Hemmingway: Depicting the rugged individualist (most of his stories), the anti-fascist guerrilla (For Whom the Bell Tolls).
5. Tolkien: For "Lord of the Rings"--a massive treatise on the corrupting influence of power, and the anarchistic depiction of Hobbit society.
6. John Stewart Mill: For "On Liberty"
7. Thomas Paine: For "Agrarian Justice", "Common Sense" and his activism.
8. Benjamin Franklin and Frederick Douglas: for their activism and their autobiographies.
9. I think we could learn a lot from MLK, the Dali Lama, and Ghandi.
10. Tucker lionized Josiah Warren and Pierre J. Proudhon as the original libertarian socialists.
11. Mark Twain and Kurt Vonnegut.
12. Herb Simon. a nobel-prize winning economist who was strongly influenced by Henry George and lent support  to some libertarian projects in Pittsburgh (without becoming affiliated with the activist groups). There are other economists who encouraged Gorbachev to use the land value tax.

Here's a list of prominent anarchists and left-libertarians. I'm not thrilled about many of the people on this list because they don't seem to have anything to say to moder American society. Much of their work is inaccessible to the moder American middle class -- either too academic, too foreign, or too grounded in the experience of the proletariat.

We may be able to draw some names from the technology crowd:

• Stallman for free software
• Neal Stephenson for Cryptonomicon
• People involved in cryptography, such as Phil Zimmerman (PGP)
• Jimmy Wales for his emphasis on transparent and voluntary organizations.

... big thinkers like Adam Smith, Thomas Jefferson, Ayn Rand, and the like ...

May I suggest that Thomas Jefferson be excluded from consideration, along with any other so-called "liberal" or "libertarian" who unrepentantly presumed to dominate his fellow human beings and force them into an abject condition of chattel slavery?

As for genuinely libertarian heroes, off the top of my head, I'd like to recommend Thomas Paine, Henry David Thoreau, William Lloyd Garrison, Wendell Phillips, Frederick Douglass, Sarah Moore Grimké, Elizabeth Cady Stanton, Lysander Spooner, Stephen Pearl Andrews, Ezra Heywood, Angela Tilton Heywood, Benjamin Tucker, William Graham Sumner, Mark Twain, Dyer Lum, Voltairine de Cleyre, Emma Goldman, Randolph Bourne, Murray Rothbard, Karl Hess, and Samuel E. Konkin III.

For what it's worth, to-day is the 200th birthday of Lysander Spooner, one of America's foremost radical libertarian heroes.

Good idea on Jefferson.

What I'm essentially looking for is someone who, if not immediately recognizable as "libertarian" and probably "left-leaning" or at least "not your usual libertarian," would be Wikipedia-able and very quickly demonstrate the same message.

Just picking out one of the names mentioned, Mark Twain, the individual has clearly anti-statist/anti-war views and is an inspiration for the movement, but he's known for so much more and it might confuse people.