Left 4 Dead. It stars the game's only female survivor, Zoey. We're not sure why someone would want to combine zombies and copious amounts of gettin' it on (death isn't exactly sexy, amirite?), but, hey, "dead" and "head" rhyme, so we can understand how someone came up with the idea. The thing that we're still stuck on is the why.
For a full breakdown of the plot, you'll want to check out our synopsis here.
[Note: any and all comments containing links to the *ahem* "film" will be deleted -- so don't even think about it. Hugs and kisses, Joystiq.]