Omeimo2 11:
Hell yeah, Dat Ayase vs. Kuroneko catfight. Bonus for random chuunibyou fight animation.
What I think is most brilliantly insidious about Oreimo is that at first you start out repulsed by the basic concept of the story, and then slowly the characters grow on you, and then you start liking the show, and then you start enjoying these fights that everyone seems to get into over Kyou-chan. It helps that Kirino starts out being an unbelievable abusive little bitch but softens considerably, following the standard tsundere character development path. By this point you're more or less used to Kirino being tsundere for aniki, such as it is.
Oreimo has grown into a parody of a harem story but the harem itself seems perfectly normal, if you consider having your own little sister in your harem to be normal. And after you've watched Oreimo enough, maybe you would. The other members of the harem are entertaining too, with chuunibyou Kuroneko, yandere Ayase, poor neglected childhood friend Manami, and the currently absent loli Ria. Kyou-chan covers all the bases with his harem, and his harem abuses him sufficiently enough that he's too cowed to dare choose any one of them for fear of being killed by the others like a good helpless harem lead.