Look, if you haven't seen Lifeforce, you're missing out. That's all there is to it. It's a movie in which vampires from space come to Earth and screw everything up. Oh and Mathilda May is the female vampire and spends the majority of the movie naked.
Naked chicks aside, I love Lifeforce because of the effects. They're absolutely insane and I love the zombie vampire puppet that appears very early in the film. The movie also has a ton of exploding miniatures, which if you've seen A Final Hit, you should know is one of my personal fetishes.
I can't explain Lifeforce in detail because storywise, it might be a boring movie. However, it's Tobe "Texas Chainsaw Massacre" Hooper making a movie about space vampires with awesome effects. I don't think I need to justify this selection any more than that.