I liked Kaichou wa maid-sama :)
Nodame Cantabile is good. The male isn't quite as strong/arrogant but is still pretty cold etc. Plus it has great music :)
Something like Vampire Knight, or even the one about a Salaryman who also fights crime if there's a love interest there.
It's hard because all the anime I can actually remember involves either homosexual love stories, guys who are more whiny than dark and mysterious, or ones where the women are the ones who need to be changed. Try just browsing the romance anime offered on sites like Animefreak until you read a description that interests you.
There's an anime called "MM!" . The guy isn't cold-hearted, but he is a masochist and the female love interest is afraid of men, so it does make for an entertaining story.
Others that don't 100% fit your needs but you might be interested in: Chobits, Elfen Lied, Full Metal Alchemist, He Is My Master, The Wallflower, and This Ugly Yet Beautiful World.
Kodomo no Omocha(Kodocha) and Gakuen AliceThey are similar in some ways though. My favorite anime is Gakuen ALice and my second is Kodomo no Omocha. They both have a cold guy and he likes a cheerful girl after the girl helps him. Hope you like them :D
it might be a little late now... but one that i TOTALLY reccomend would be:
La Corda d'Oro
its a sort of reverse harem in it, but one of the guys "Len" is very anti social and cold, and then when the girl comes along she touches his stone cold heart... its adorable, they would make the bestest couple! - you must watch this!
Kamisama Kiss(Kamisama Hajimemashita)
Nanami Momozono is alone and homeless after her dad skips town to evade his gambling debts and the debt collectors kick her out of her apartment. So when a man she's just saved from a dog offers her his home, she jumps at the opportunity. But it turns out that his place is a shrine, and Nanami has unwittingly taken over his job as a local deity! Nanami has all kinda of new responsibilities she doesn't understand, dangers she's unaware of, and a cranky ex-familiar who's... actually pretty hot. What's a new-fledged godling to do?
hope u like it because i loved it :)
Gakuen alice( BEST ANIME I HAVE EVER WATCHED IN MY WHOLE LIFE! But if you read the manga though, its pretty sad.)
im finding this kind of anime too cause i just recently watched Ghost Hunt..pretty scary if you watch it at night but i like the guy!...then there' s this phychic detective yakumo...just sharing ^.^
kaze no stigma