I voted for Saber, Rin and Archer.
Saber- She is cute, naive, but she has a great heart. She is definitely a heroine, although Shirou is trying to change that.
Rin- She is cool and collected on the outside, but she is a very nice person on the inside. She is also very pretty. I can say more, but I think that's enough for now.
Archer- His lines when he used UBW were so cool, just those alone earn him a spot.