I voted for Toussaud, but was going to mention Delicate Vine as well. That filly was awesome.
Toussaud though? I know I've said it many times before, but to this day I still think she was one of the most electrifying horses I've ever seen run. Her turn of foot must be seen to be understood.
Here is her Gamely win
http://www.youtube.com/watch?v=yHKNF132Zao
About ten years ago, Frankel was asked who his best fillies that he ever trained were, and he replied that they were Toussaud, Delicate Vine and Jolypha.
Of course, he's had some awesome ones since then, but those first two were no brainers.