I think my vote has to go for Sergio Leone’s magnum opus Once Upon A Time In The West. For all of it’s flaws (it takes two or three viewings to really make sense of the complex story and fully grasp the machinations of the characters), the nearly 10 minute opening scene is truly memorable; the three assassins taking their places in the decaying train depot, each waiting impassively for the arrival of “Harmonica”. “It looks like we brought one horse too few.” “No, you brought two too many.”
A close runner up is Sam Peckinpah’s The Wild Bunch; a setup bank job (interspaced dramatically with the credits) in the middle of a town full of children and temperance campaigners. “If they move, kill 'em!”
A third is Hitchcock’s Rear Window, with its voyeristic pan around the neighborhood. And Thelma Ritter (Stella, the nurse) gets the best lines: “She sure is the ‘eat, drink and be merry’ girl.” “Yeah, she’ll wind up fat, alcoholic and miserable.”
I hate to delay a mention of Raiders of the Ark–its exended chase sequence tops anything offered by the Bond films for action–but it has to wedge in at number 4. (The opening sequences in Indiana Jones and the Temple of Doom and Indiana Jones and the Last Crusade, while not making it into the top five, are still the best parts of those films.)
Coming out to a nice round accounting of digits on the hominid hand, Kubrick’s nearlhy pornographic opening scene in Dr. Strangelove: Or How I Learned To Stop Worrying And Love The Bomb, consisting entirely of stock footage of a B-52 performing a mid-air refueling operation, sets the entire tone for the movie; starkly playful, groundedly satirical, maddenly realistic. You don’t know whether to laugh or worry that General Turgidson is, in true Curtis LeMay fashion, justifying a disarming first strike as a protective measure against the reciprical action by the Soviets in response to Attack Plan R, all the while enthusiastically chewing his gum. “Mr. President, I’m not saying we wouldn’t get our hair mussed. But I do say no more than ten to twenty million killed, tops. Uh, depending on the breaks.”
There are, no doubt, others that I’ve missed or have been forced, in limiting my selection, to omit. The teasers in Goldfinger (“Shocking…positively shocking.”) and The Living Daylights (the training mission to infiltrate the Gibralter radar installation turning into an assassination…“Double-oh-seven here; I’ll report in in an hour…better make that two.”), while not perhaps qualifying as greatest opening scenes were certainly iconic. What else?