This is probably the most "shonen"y arc in the traditional sense, but I think I really like how complete and amazing it felt to see the growth and intelligence Gon and Kilua had and applied to their battles. Things like Killua's yoyo and their attacks coming into their own was great. In addition, it was beautiful when Gon talks of Killua being his best friend.

Then awesome side stuff like Killua taking and passing the exam with ease is fun and cool too. (and seeing the guy from Yorknew was interesting as well! I like that Togashi doesn't forget that stuff.)