I'd say either Hikaru, or Kyouya.
Hikaru: because they did have their so called "first date" and Hikaru had feelings for her in his own way though.
Kyouya: It's quite possible for Kyouya to end up with haruhi on their reactions on teh episode where they went to the beach and haruhi and tamaki got in a fight.
BUUUUUTTT, technically it's Tamaki. And i know everyone knows why.