I voted for Saber mainly because she was the first character that got me into Fate/Stay Night back when the game was initially released. She also strikes a chord with me due to her similarities with Arcueid from Tsukihime.
However, 2nd place would have gone to Rin (ice cold princess type but cute at times) but due to the animation of Sakura (cute!!!) in the anime and knowing her story in Heaven's Feel she takes 2nd place now.
