9. A Seagull Invaded The Closing Scene - Barton Fink
The Coen Brothers' superb psychological thriller Barton Fink ends with one of the most memorable images in their entire filmography - courtesy of veteran DP Roger Deakins - when Barton (John Turturro) wanders onto a beach only to see a beautiful woman resembling the one from the iconic photo featured throughout the film.
To top it all off, in the final second of the film a seagull is seen flying into shot and suddenly falling into the sea, apparently dead. As much as this might seem like an intentional blackly comedic concoction by the Coens, it was actually completely by happenstance.
As it turns out, this wasn't planned in the slightest - the seagull simply divebombed into the sea mid-take and the Coens liked it enough that they not only kept it in, but abruptly cut to the credits afterwards to give the impression the gull was dead. Perfection.