Yeah, all of my favorite pairings are just completely out there. Then again, this show put so many weird couples together that I don't think ANY pairing could really be "out there". So here we go. Flame away.
Giles and Anya
Honorable mention goes to Spike and Faith (oh come on, how hot would that be?)
I feel like Giles and Anya are the two most intelligent characters on this show. Plus, they're my two favorites, so I'm a little biased. But I honestly think they'd be adorable together. Giles definitely appears to admire Anya's abilities when it comes to knowledge of the supernatural and often looks to her for expertise. He also realizes her business acumen pretty much immediately. For her part, Anya seems to take a genuine liking to Giles. And I can't really say the age difference would be a difficult one to manage here--after all, Anya is over a thousand years old.
I mean, come on, Giles seems to be destined for perpetual romantic misery, and Xander and Anya didn't exactly work out because, mostly, he was too immature for her. And while Giles can often be made uncomfortable or joke about Anya's lack of social graces, he also appreciates her skills and knowledge in a way that Xander never really does.
Also, there are these things, from the season six finale "Grave":
What did you do? GILES
Contained her and her powers within
a binding field. It puts her in a
kind of stasis for the time--
You've cut your hair.
I colored my hair. Again. I'm
Yes. I noticed.
Giles? Giles. Don't die. Not yet.
I... There are... I need to tell
(tears start to flow)
Thanks a lot for coming. I mean, it
was nice of you to teleport all this
Though, in retrospect, it might have
been better if you hadn't come and
given her all that magic that made
her ten times more powerful... that
would have been a plus.
(barely a whisper)
It's not over.