I'm gonna have to say Luke for one. Just his character, unique in my mind. And come on, you can't really hate Zorua, cute yet strong and tricky, loveable over all. I also am taking a liking to his clothing, sort of a steam-punk-ish style to it. He has to be my favorite.
Also, they made Cilan have an interesting character. I like seeing the characters from the game being transfered into the animé.
Trip makes a good rival, although his hair is the color of puke... It's the truth.
The name gag with Stephan is quite comical, and I absolutely love his taste for fighting types (Sawk FTW!)
As for Ash, nothing needs to be said here, we all know him extremely well.
Moving on to Iris, another game tranfer to animé. I like how her character is turning out, she has interesting Pokémon. Absoluetly adored Excadrill's stuborn personality in the begining. Oh and her hair is ridiculous! Well... Just about all animé hair is... So I take that back.
Now for Burgundy. Her name has a relation to wine, both Japanese name(Cabernet) and American name, I like that reference, as Connoisseur and Connaisseuse come from French origin. But I have one problem the names, her hair is purple, Burgundy is also a color (Commonly of color of wine), it's a redish color(So is cabernet). Red and purple... Not even close colors. Well purple is the color of most grapes, grapes are made into wine, so I can see the relation there. I feel as if her character is still developing a bit, so I can't seriously comment on it.
As for Bianca (Another game transfer) , I like her personality regarding her role in the game and the animé. She is exactly how I imagined her as I played the game. EDIT: And I agree with her being the female version of Barry.
Finishing off with Georgia. I feel as if I haven't come to know this character that much. We get the jist of her, but I would like to see her evolve (Not literally) in character. Iris needed a rival and Georgia is just a perfect fit for the role so far.
Now that I've expressed my feelings for all of them I'm still going to have to say Luke is my favorite. I just adore his character!