Who are your favorite male and female characters in Arms and the Man and why?
First, my favorite characters may not be your favorites; this is something you really need to decide for yourself as you read the play.
That being said, my favorite male character is Captain Bluntschli, the lead male character. In many ways, he acts as a mouthpiece for Shaw himself. He is intelligent, pragmatic, and cynical, albeit with a somewhat romantic streak when it comes to charming young women. Unlike the other characters in the play, he does not view war through the lens of Romantic literature, but as a profession, and despite (or perhaps because of) being a soldier is actually more critical of the causes and practices of armed conflict than the other characters in the play.
For female characters, I don't really find any of them admirable. Louka is petty and spiteful and Catherine Petkoff is silly and snobbish. Raina is meant to be the heroine of the play, and does exhibit a combination of being open to new ideas and kindness and thus is really the best of the female characters, but her role is to a large degree to be educated by Captain Bluntschli rather than to stand as a strong and independent character on her own. She strikes me more as a rather impetuous adolescent (albeit a nice one) than as someone I can really admire.