Not sure how I've failed to chime in on this thread.
Best round is the 70 (-2) I put up last August at Streamsong Red, to win my flight (1st flight but not the open flight, forget the name) at the two-day Streamsong. I hadn't done anything particularly well that week in practice rounds or the day before at Blue, but had at the same time managed to avoid all the big numbers as well. On the day in question, I birdied 3 and 7, made an all-world up and down par on 8, birdied 10, bogey'd 11, then parred in (making ~6' par putts on 17 and 18). Out of body experience, and without an doubt the best I've ever hit a golf ball.
Most memorable round is a three-way tie. Both of my holes-in-one have come when playing with my dad - #13 at Avery, and #7 at Star Ranch. Then in a recent member-three-guest tournament with three gents on this thread, one of those gentlemen split the fairway with a long, soft draw. Just an excellent all around swing. And I put it 40 yards past him. The ball hadn't even apexed yet and I hear one of the other guys say, behind me ... "that was a dick move."
Similar conversation always happens on the "best course you've ever played" topic. I've never been to Bandon Dunes, but have been fortunate enough to play some PGA tracks, even a few major-championship tracks. Only Olympic in SF has left me speechless. That's an incredible golf course.