A Hand Shake (1892)
This film clocks in at just four seconds and features William K.L. Dickson and William Heise shaking hands.
From what I've read this film was never released to the public and was basically just a test for the camera. Of course it's impossible to judge this like a film of today but there's no question there's something special about watching the footage well over a hundred years after it was made. As a film buff I just love watching this old footage even though there's certainly nothing special about it other than its age and how it would slowly help shape motion pictures into what they would eventually become.