I would have to say Jana Novotna - Steffi Graf, Wimbledon final 1993.
Until she choked in the third set, Novotna had the best performance I have ever seen, she was just amazing, doing everything perfect.
The serve, not many aces, just great placement and bouncing very high, so forcing Steffi to return high ball that Novotna could easily catch at the net.
Her volleys were just incredible, not only the touch but also she was guessing every passing shot, every lob, she was moving all across the net to reach the ball.
And the slice backhand approach shots?, deep, with the ball barely bouncing.
Very few times I've seen Steffi with no answers, and it wasn't that Steffi was off or anything, Novotna just had one of those days. Unfortunately she messed up in the third with one of her usual chokes