Can't talk about the entire Open era but I'd like to mention Myskina vs Davenport match from the 2004 YEC.
It's such a pity nobody recorded that match and put it on the web.
That was the third match Davenport and Myskina played in the span of four or so weeks.
On the superfast Filderstadt courts Lindsay just rolled over her but Nastya actually put up a decent fight in the second set. Moreover, after the match she said she seemed to finally figure out how to beat Linds. It sounded kinda
considering she had just lost 4th match in a row to her without winning a single set. But she did
beat Lindsay the following week at Moscow.
Using the superslow Moscow courts to her advantage she made Davenport hit too many shots, taking Linds out of her comfort zone. Myskina run a LOT in that match but each time managed to put herself in position to neutralize another bomb Linds was throwing at her. Still, many believed the loss was a result of "bad day in the office" for Lindsay who, btw, wasn't feeling well that day.
In a couple of weeks they met again, this time in a round robin match at the YEC. Lindsay was coming in as the overwhelming favorite : she previously destroyed Dementieva 60 61 while Myskina just suffered yet another heartbreaking loss of 2004 (this time she squandered a 64 30 lead against Serena).
Myskina's only option seemed to be turning into wall, chasing every ball down and eventually frustrating Davenport with her superb defense. But Nastya, to a great surprise, chose the opposite tactics -- she decided to play offensive and match Lindsay from the baseline shot for shot. And, what was even more surprising, Myskina built her attacking game around her less reliable shot -- forehand.
I never saw Myskina serving that great and hitting such huge forehands. On some occasions Lindsay looked lost in disbelief that she was actually being outhit by someone who, on paper, should have been running three meters behind the baseline and trying to put the ball back down the middle.
Too pity Myskina was never able to replicate such a courageous performance again. For the rest of her career she turned into a mixture of a pusher and an UE machine coming to life only during grass court season.