Monstrous Regiment by Terry Pratchett
Young Polly Oliver (yes, she knows the song) chops her hair off, dons a pair of trousers and attempts to learn how to swear, burp and fart in public without shame. Yes, that's right, she's enlisting in the (all-male) army, in a war over territory, and the Clacks towers. This is the end of the war though, and all that the recruiting party can muster is a vampire, a troll, an igor, someone who shouldn't be allowed near matches, and someone who talks incessantly to the semi-mythical "Duchess", who is the leader of the country they're from. Still, they're on the winning side- aren't they?
Again, this was Pratchett at his satirical best. I especially like the war reporters and the description of the cartoon in the paper. It sounded exactly like 18th and 19th century newspaper cartoons. The reference to war films is brilliant too- I've never seen the film in question (which I won't name for fear of it being a spoiler) but I don't think I'll be able to watch it now without laughing!