Crossover Fan Fiction

I'm looking for crossover recs. I'd love to see a crossover between House and Grey's Anatomy. Other crossovers I'd like to see Buffy(Angel)/Heroes or anything with any of two or more of the following shows: Buffy, Angel, Lost, Heroes, House, Grey's Anatomy, Stargate SG-1, or Dr. Who. (Please no fic that focuses on Buffy Summers, Buffy/Angel, Spuffy, Jack Shepherd, Kate Austin, Allison Cameron, and/or Meredith/McDreamy.)

I'm going to start to do this more often, because really, I feel that I should share the wealth when I happen to stumble across it.

Fandom: Buffy the Vampire Slayer/Harry Potter
Title: The End of the Beginning
Author: Mariner
Rating: PG-13
Genre: Drama/Action/Adventure
Spoilers: None
Summary: London, 1981. Rupert Giles and Ethan Rayne thought they understood magic -- until the night they saw a glowing green skull in the sky above a quiet London street.
URL: http://www.fanfiction.net/s/1375393/1/

Why I Like This Fic: This is the first, I repeat, the first, Buffy the Vampire Slayer/Harry Potter fic that I actually made it past the first chapter of, enjoyed and kept on reading. The main Buffy players are Giles and Ethan who interact with the Wizarding World in the days before Harry became The Boy Who Lived, back when wizards still said the name "Voldemort," and didn't shush one another and whisper, "You Know Who." Most importantly, it works. It works in both universes, in both timelines, and it never turns into an alternate reality because it doesn't have to. It has nothing to do with Giles having once been a Hogwart's student whom lost his wand or gave up wizarding in favor of Watching, there are no surprise familiar relationships or connections. There is no All Knowing Wizarding Omnipotence, No Magic Is Universal Assumption, and No Giles Wandering About with A Wand.

Example of fic: So many good scenes, how to chose just one?

( Snark, works well under any circumstances )

. . .

Go, read this fic. Tell the author how wonderful it is. And please, point me in the direction of other fic of this caliber.

(Edited to add the link that I forgot!)