Genre Crossovers

I like the idea of taking two kind of tired, slightly worn-out genres and blending them into something new. Terry Pratchett does this with satire/social commentary and epic fantasy. The writers of Pluto Nash attempted it with crime drama, comedy and science fiction and failed miserably.

Just wondering if anyone has any more examples of genre-mashing, whether brilliantly done or painfully unsuccessful. Also, are there any combinations you'd like to see but haven't, or any you'd like to write (/plan to write/are in the middle of writing)?

Pop into the comments and let us know.

I'm currently working on a post-apocalyptic(ish) fantasy road-trip thing. I like what I've written so far, but the going is slow. I think that has a lot to do with trying to keep the world and characters true to themselves but inclusive of each other.