6. The Fly (1986)
The "Sad" Ending...The Fly has one of the all-time, "Good Jesus, no," endings ever filmed, because it graphically depicts what happens when a fly-man hybrid finally gives over to his inherent fly personality traits, and tries to murder you. Having been rendered half-man, half-fly by way of a teleportation experiment gone horribly wrong, scientist Seth Brundle assaults his ex-girlfriend, Veronica, and her sleazy ex-boyfriend, Stathis (this poor guy gets his leg melted off), before she realises that she has no choice but to shotgun him to death. Which she does.
The Abandoned "Happy" Ending... The "fade out" that comes after Veronica has blown the mutated face off her once true love has always seemed a bit sudden to me, but one can't deny it's an effective way to end this particular flick: there's nothing else to say, right? Apparently Cronenberg considered that there was, though, given that an epilogue was shot which explained how Veronica
wasn't carrying Seth's fly-baby - it was actually Stathis'. Test audiences weren't pleased with that ending, though, 'cause Stathis was a head for most of the flick. Shotgun ending it is, then.