This fic is not mine, but I found this epic gem a day ago...and it's possibly the best fic I've ever read. Not only is it mind blowing in the way it is presented, but the length is over 250 pages, spanning 18 chapters. The writer based it off of the end of the Anime, (which can hook you from the start, since we all know that the Anime followed the Fate route ending) and it's a great read for those who are a fan of SaberXRin. Even if you're not a fan of this pairing (I was neutral) it makes you like it.
There is adult content in it, so just know that some area's are M rated.
Too large to post individual chapters here, so take the link (and bookmark it if you really like it. ) )
http://www.geocities.com/cyberan0/fsn_kq_index.html (Nice cover pic too )
Also, some chapters point out BGM to play along while reading, those can be found on the same page.