The Voices is a horror movie with dark (very very dark) comedic elements. I think I bought my copy new.
Even my synopsis gets into spoiler territory, but I felt it was necessary in order to get across how dark this becomes.
Review:
Jerry is a cheerful guy who loves his job working at a warehouse in a bathtub factory. He's had some problems in the past, but he's now seeing a court-appointed psychiatrist and is doing great...except that he doesn't have any friends or a girlfriend, just his dog Bosco and cat Mr. Whiskers. But then he falls head over heels for Fiona, one of the office ladies (in Accounting, I think? I can't remember) at his company.
Unfortunately, she isn't nearly as enamored with him as he is with her and stands him up when he invites her to dinner. He sees her later when she's having car trouble and assumes that this is what kept her from joining him for dinner, so he picks her up and starts taking her home. Unfortunately, he hits a deer, which goes through the windshield. He hallucinates the deer begging him to put it out of its misery, which he does, slitting its throat with a knife, much to Fiona's horror. Fiona runs off and Jerry goes after her, accidentally tripping and stabbing her. He then "puts her out of her misery" as well, stabbing her repeatedly while apologizing.
When he goes home, Bosco, who Jerry hears as the good part of his conscience, tells him to go to the police. However, Mr. Whiskers, his darker side, doesn't think he should feel bad about killing. Although Mr. Whiskers pretty much wins this battle, there's still the issue of Fiona's body, which Jerry eventually collects, dismembers, almost entirely stores in Tupperware containers throughout his home. He keeps her head in his fridge, where it continues to talk to him.
This is, of course, not the end of Jerry's troubles, as various people start worrying about and looking for Fiona, and Jerry begins to fall for Lisa, one of Fiona's coworkers.