I will contribute my opinions....
1- Merion - this course makes you think about every shot to be taken, the rough is very unforgiving, the greens are very demanding, and precision is required at all times. I had never felt that laying up safely was a better option, on so many holes, as at Merion.
2&3 - a tie between Olympic and Oakmont - Olympic with its' anti-pitched fairways and tough greens; and Oakmont can just be all-around tough.
4- Whistler - this course just plain stymies me...lots of "traps" if one isn't careful.
5&up - all of the other courses....I even LOVE Royal St. Georges...won a Ready- Go there recently in very high wind conditions....the place seems to suit me. And Cabo seems conducive to low scoring rounds, with flat greens and a general ease of getting around the course....
JMHO....for what they are worth.......
...see you on the course....
Immpy