What about Dr. Strangelove? Stanley Kubrick did not like letterboxing, approved of a mixed aspect ratio transfer in later years, and used copious amounts of "full screen" stock footage in his film.
Speaking of Kubrick, one of the more hilarious pan & scans was the old fullscreen version of 2001 you saw for years on TV: the scene where astronauts Bowman and Poole discuss Hal's fate in the pod.
You're supposed to see both guys at the left and right of your screen, with Hal in the middle, but in pan and scan you cut between each speaking actor without seeing Hal, who we all know was lip reading all the time.
Also, supposedly, in 'The Shining', you can see the helicopter blades at the top of the shot when the camera settles on the Overlook Hotel at end of the opening credits. You can also see the helicopter shadow very clearly during those cool sweeping shots of the Volkswagen during the credits.