Hana Yori Dango.
http://myanimelist.net/manga/877/Hana_Yori_Dango
http://en.wikipedia.org/wiki/Boys_Over_Flowers
Tsukushi actually becomes a target for other students who bully her after she receives a card from the F4. Tsukasa is the leader of the F4 and it's because Tsukushi stands up for her friend Makiko after she has a run-in with Tsukasa that she receives the card.
So, the two basically hate each other at first but after Tsukushi attacks Tsukasa in the hallway, giving him a red card of her own, he becomes attracted to her strength and personality.
It's an old one, but it's pretty good.