Sometimes taking two genres and putting them together just makes everything that much more wonderful. And sometimes... it's just they clash, like stripes and plaid. What's the absolute best, or very worst, combination of two genres that you've ever witnessed?

Please include a picture, clip, poster, comics panel, book cover or other representation of your best or worst mash-up. And please mention the name and why it was a great (or terrible) combination of two genres. Thanks!

Top image: Firefly and Cowboys and Aliens. They both combined "Western" with "science fiction," only one of them was a lot more successful than the other.