I just finished reading Far Beyond Normal and Return to Normal by jAkL. They're Buffy/Stargate crossovers, and utterly fucking amazing. A bit bleaker than I usually like it, and "show, don't tell" is thrown right out the window, but still.
Both fics won "Best Crossover", "Best Portrayal of Buffy", and "Best Portrayal of a Villain" at the Crossing Over Awards (the first last year, the sequel this year). They deserve the awards. I honestly think that, together, they make the absolute best genfic I've ever read. I'm not even sure I'm exaggerating on that.
You should go read them--even if you've never seen anything in either series.
Far Beyond NormalBuffy did not survive her confrontation with the First. Fortunately, Buffy has never been one to let death stand in her way...
Return to NormalBuffy wants another shot at the First. Not everyone thinks this is a good idea. Especially since the First knows she's coming.