This might fit too.
It's a new fave too.
Denial by The Enemy of Reality
Summary: Forced to be close together for an infinite amount of time, it stands to reason that mortal enemies would drive each other insane. But when it comes to a self-righteous, uptight slayer and an irritating, chipped vampire, there is no reason. This story, set just after S4, is full of banter and innuendo, so read on if you are interested. Also, Riley left to roam the jungle a little early so he isn't in the picture. Complete