Fanfic Great story
Alright I noticed that Fate Revelation Online has no reviews, so I thought I might as well be the first one to post. (Especially since I made an account just to do this) :)
Fate Revelation Online is an amazing story that I enjoy that has a fast update rate and an author who is willing to correct any mistakes us readers find.
On top of that it has very enjoyable character interaction in which all the characters are very recognizable for who they really are, for example Shirou and Illya interactions, unless you count HF route she is never redeemed hence she is still the cheerful psychopath we all know and love, and she is actually working with Kayaba in keeping the game going because he is going to make a new body for her that will expand her lifespan past the year it should be.
Overall this story is a stunning peace of work that I loved, I recommend reading it. (Now I just need to figure out how to add tropes to the page that way I can add a ton more than the few it has)
Fanfic An excellent crossing of the two
Normally you wouldn't think that Sword Art Online and Fate Stay Night were compatible, due to the genres being grounded into two different sections and the mechanics. And then you read this fanfic and learn otherwise.
Without outright spoiling things, the author has not only added your favorite characters from the two series, but had them mingle without the typical harem hijinks that follow. While the focus isn't on romance at this point, the plot is solid and the villain of the piece isn't some lunatic who decided to wantonly trap 10,000 people because he wanted them to play the game as reality, nor some defective priest who wants to see the world burn. The progression is somewhat slow-going, but it allows you to focus on the growth of the characters and even shallow characters prior have been given some depth.
And then there's the Magecraft. Rather than having the typical overpowered or nonsensical systems put into place, we can see the research done into each system used. The author's even managed to give Shirou one of the few things he typically never gains in fanfics: An education in Magecraft beyond spamming swords.
No character is truly overpowered. While Shirou and Ilya do have some advantages, because they carry over from their Fate Route counterparts, its made clear that they can't solve every problem and they are true to their personalities to the letter.