Hikaru and Kaoru were my favorite characters in this show. This was one of the first animes I saw so at the time their "brotherly love" kinda bothered me. But despite that they quickly became my favorites.
All the host club characters are interesting in their own way. But I loved the Hitachian twins mischievous care free attitude. They also had a down to earth side that I could connect to, they just wanted to be noticed, they wanted someone to be able to tell them apart. They loved to antagonize people with their games, but they mostly don't mean any harm.