The Truce by Eternal Red. But it's a WIP.
Once in a galaxy, far, far...oh, that's been done. Right then. Humankind has been at war with the Aurelians for decades. When the two sides finally reach the point where negotiation is better than annihilation, a truce is called and a treaty negotiated on the planet currently under dispute. The peace treaty is cemented symbolically by the joining in marriage of the two youngest soldiers present, thereby throwing Buffy and Spike into a relationship that they really, really, don't want.
The Green Card verse by brutti_ma_buoni
Sometime after Something Blue, in an increasingly AU Sunnydale, it's becoming clear that Spike just hiding out in a crypt or a basement isn't enough. The Scoobies still need Spike, and the Initiative's plans are bigger, and longer term, than in canon. Drastic action is required. Buffy steps up to the... altar? What happens after that changes the face of the Buffyverse. There's frivolity and angst in varying quantities as we see what this one 'simple' change has meant. 
