Two I really really like are Mrs Muir's:
Three Hearts Entwined by Mrs. Muirhttp://www.angelfire.com/folk/whenbuffysmiles/Summary: An Angel/Buffy/Spike romance. The three are thrown into a relationship by mutual needs but end up deciding this is the best relationship for them when they realize they are in love with the other two. Set after season 3 with canon rearranged to suit the story.Menage a Trois by MrsMuirSequel to Three Hearts Entwinedhttp://www.angelfire.com/folk/whenbuffysmiles/Summary: Life changes for the threesome. They have to learn to work together, and love together, as they start a new business and Angel's curse is lifted.What I think is fascinating about these two fics is that ostensibly the reason for the threesome is to get B/A together without A losing his soul. With Spike in the mix A can participate in sex with Buffy without actually 'doing it' and they theorize that they can then be together. But they have to include Spike. And as they go along, Buffy and Spike grow closer and closer, especially since he is the only one she can have full sex with.
So in a way it's a B/A pairing but not really - it's a B/S/A pairing, with B/S getting a lot of attention overall. For this reason it is not actually spuffy but is really really spuffy adjacent, so much so that I think that many spuffy readers would appreciate it. That's my opinion anyway. I really like them.

Oh, and when you click the link you need to go to 'other pairings' to get to the 'Buffy/Angel/Spike' pairing section where this story is located.