All credit goes to DoctorRadiohead on letterboxd, who created the original list.
Original description goes as follows: "Not to be confused with movies with a surprise or twist ending where audience would have some time to process the change. No. This list is for the films which have that last shot which leaves you gobsmacked and gasping for breath. Movies where the last shot 1.introduces a new twist in the narrative or 2. confirms the foreshadowed twist or 3. adds an extra bit of information in the story which changes the understanding of the forgone narrative or 4.just some [screwed] up shot which doesn't make sense but surprises you nonetheless- IN THE LAST SHOT (or penultimate for flexibility) and then fades/cuts to black".