I usually find the Hermit is my favorite card in many decks. I'm very fond of the Tarot of the Sevenfold Mystery's Hermit (I don't own the deck but I plan to at some point) now that Robert M. Place's decks come to mind, I also really like The Hanged Man (Madman) from the Vampire Tarot.
From traditional decks, I think Death is my favorite in most Marseilles (those little heads!) Hanged Man, Chariot and Strength and Marseilles Courts are also badass. In the RWS I've always liked the Queen of Wands with the black cat, Strength, The Magician, and The Hermit of course.