Gods, I'm tempted to put a gif of Giles and Buffy on the balcony and insert the dialog between Buffy and Spike on the balcony. That would probably traumatize too many eyes here, though.
In actuality, I voted Jenny. There were only 2 possible OTP on Buffy as far as I'm concerned (not that I obsess over them or devour the fanfics): Giles/Janny and Anya/Spike. (Don't worry all of you who want to rain flames down on me for saying that, I can already hear the stadium erupting into boos.

)
I voted for Jenny, but Joyce would've worked. Giles was something of a father figure for Buffy anyway, though where I first contemplated it was how it shows Giles looking wrecked as he listens to the record after Joyce's funeral that he played for Joyce in Band Candy. Giles is one of those people that many mistake as not having much in the way of emotion, but he just keeps them far under wraps, under control (as much as he can), and still waters run deep, including in passions.