Hufflepuffs and Slytherins make great couples. There aren't many of them, but they have the coolest romances ever. Lots of quarreling, lots of snark, lots of drama.
Andromeda and Ted, Harry Potter. They are the original specimen, how they ever became friends I wish I knew.
Ned and Chuck, Pushing Daisies. They're always bickering, but always forgiving. He doesn't really understand her ambition, and she doesn't understand his complacency, but they still love each other.
Chad and Sonny, Sonny With a Chance. Pride can be a turn-on. As can "stupid cute."
Percy and Annabeth, Percy Jackson and the Olympians. "I am never, ever going to make things easy for you. Get used to it."
Margaret and Thornton, North & South. Margaret's disgusting moral high-ground and Thornton's thoughtless ambition balance each other out. (Although he's better looking then a bulldog.)
Zoe and Wash, Firefly. She's a little scary, but he's really nice and understanding. Wash is like the opposite of Mal, maybe that's why she loves him.
Sophie and Howl, The Moving Castle Series. "They were living- somewhat quarrelsomely, it must be confessed, although they were said to be happiest that way. "
Well, goodbye cruel world.