Here are my favourites:
Terry Gilliam - An absolute genius when it comes to the surreal. Starting off as the cartoonist for Monty Python, he then helped write Monty Python and the Holy Grail and Life of Brian, and he then brought Brazil (My favourite film of all time), Fear and Loathing in Las Vegas, Jabberwocky, The Fisher King, Time Bandits and Baron Munchausen to the screen. A legend, plain and simple. Even Dr. Parnassus was a good film.
Godfrey Ho - The man behind 85% of the bad movies I have owned or watched. Just watch this
Sergio Leone - A Fistful of Dollars, For a Few Dollars More, The Good, The Bad and The Ugly, Once Upon a Time in America, A Fistful of Dynamite. Yep. Legend.
Stanley Kubrick - Spartacus, The Shining, Full Metal Jacket, Dr. Strangelove, 2001, A Clockwork Orange. Yep. Legend.