The release of the Alien prequel Prometheus got me thinking about Mario Bava, and how the endings of both Planet of the Vampires and Rabid Dogs are predicated on shock/surprise.

I think Rabid Dogs works better, because it's set in this world and the actions of Riccardo Cucciolla's character are consistent throughout, so that watching it a second time you see new resonances in the performance and the direction. In Planet of the Vampires, by contrast, the these are humans - oh no, they're not, despite their names - moment only works the first time.