This is all Weiß Kreuz, and all Slash.
http://www.farfarello.org/fanfiction.html -- All of her fics, specifically 'The Dust Dancers'. Her pairing is Schuldig/Farfarello. And they're epic-length!
http://www.angelfire.com/anime4/patternsofblood/mamifics.html -- Again, you should read
all of her fiction. I love 'Eyes On Me' and 'Cry Me a River'. She writes many Schwarz-centric pairings and some Weiß ones. Again, a lot of epics, but some are long one-shots like 'Cry Me a River'.
http://www.trowaluvsduo.net/weissweb/weissfics/tdindex.htm -- She's written a number of good fics. Read 'Something Me in You', then the two fics that come after it. They're all epics.
And that's all. Go read them. I wouldn't lead you wrong, even if you don't know what the anime Weiß Kreuz *is*, do a Google.com search and learn about it so you can read and inderstand these fics.
For Weiß Kreuz info, specifically the assassin team Schwarz:
http://www.geocities.com/tengoku_mimizuku/lastchaos/ -- If you're interested, just take it from there. Download the eps on kaaza lite, or buy them off amazon.com (Under the americanized name 'Knight Hunters' though the true translation of the German title 'Weiß Kreuz' is 'White Cross'). Weiß means White, Kreuz means Cross, and Schwarz means Black. And you make the ß symbol by holding down on the ALT key, hitting 2 2 5 and then releasing the alt key.
Yes, I am obbsessed. the characters are as follows:
Weiß-
-Aya, codename Abyssinian.
-Ken, codename Siberian.
-Yohji, codename Balinese.
-Omi, codename Bombay.
Schwarz-
-Crawford, (precognitive), codename Oracle.
-Schuldig, (Telepath), codename Mastermind.
-Farfarello, (inability to feel physical pain), codename Berserker.
-Nagi, (telekenetik), codename Prodigy.
I've probably confused you.
sigh please go
http://www.geocities.com/tengoku_mimizuku/lastchaos/ there for more coherent information.