An obvious one that must have been done before: Giles playing Cyrano to somebody's Christian, wooing Buffy's Roxane. Obvious choice is Angel (though the high school timeline makes it problematic). Spike would be a comic choice for the stupid-but-handsome Christian. Happy ending, please.
Or another take: Giles writing letters to Anya for Xander. Or Giles writing to Xander for ... choose for maximal comic effect. Buffy, for instance.
"The Replacement", Giles gets hit.
I'll probably write the first one. I have a couple more ideas about how to do that, and what happens. Am also working on tagfic and the Valentine's Day prompts y'all gave me ages ago.