Somebody mentioned it before and I agree: Fahrenheit 451 has a brilliant opening. Because the story involves a society in which literature is illegal, Truffaut opens the film with "spoken" credits. No text is displayed. It's awesome.
My favorite opening is "Monty Python and the Holy Grail." After that crazy credit sequence, they spend three minutes arguing about coconuts and European versus African swallows before Arthur can even get on with his quest. Great silly opening.