These are my favourite:
Better Late Than Never by susThe Slayer knew there would be repercussions if the Scooby Gang ever discovered how close she and Spike had become. She needed time to find a way to fit the illicit relationship into her life, and convinced Spike to keep their love a secret for now. Unfortunately, no secret is safe on the Hellmouth. When the fit hit the shan, the Slayer once again sacrificed herself and her own happiness in order to keep those around her happy. Until one day, when saving the world, and maybe even saving the Slayer, all came down to one peroxide vampire and the strength of his love.To Wed A Vampire by Joyful Dayz(sorry don't a have a summary for this one, but in general, Spike claims Buffy to increase her power)
and it's sequel:
A New Day by Joyful DayzEmbracing Darkness by SlayrGrlThere is one thing that Buffy Summers has feared since she became the slayer. It is her worst nightmare, and now she must face it. After rejecting the Shadowmen's offer to make her more powerful Buffy realizes that she isn't strong enough to win in the fight against the First. Now there is only one option left to give her the strength she needs. To win Buffy must die, but can Spike bring himself to damn her? Deserving by KaylorinBegins directly after Grave. My season 7. Loosely based on spoilers and speculation available at the time. Buffy has begun her life after the events of Tara's death. Spike has changed for her. There is a new BB that brings Buffy back to her roots as The Slayer. Sorry I can't give you links for them (in a rush to go), but those should be here on SR or can be found via google
