[quote=Masaki Haruna]
there's a route in Fate where Saber's a boy.
[/quote]

As someone who has played the original VN multiple times, no there is not.

If you mean the Fate/Prototype OVA thing, then that was just something made out of Nasu's random notes whilst he was still developing the story. Arthur was dropped pretty quickly, and for pretty much the entire time Arturia has been Arturia and I would have her no other way.