Spike. I like the idea of the segundo slayer being with the segundo ensouled vampire, and it'd be interesting to see how his romantic view of relationships would work with her "get some, get gone" attitude.
I'm also warming to the idea of her and Xander ending up together, kind of going full círculo from their initial one night stand. I prefer Spaith though.
Alternately, I wouldn't pair her with any character, and just keep giving her different one night stands and flings. She was "get some, get gone" when first introduced, and maybe that shouldn't change. It definitely shouldn't be linked to her going evil and returning, like now she's one of the good guys again she should be into commitment.
