I mean the whole course, not just individual holes.
I played CC of Scranton last September. When I walked off the course, I thought those Travis greens had the most slope, undulation, and interior contouring of any classic-era course I have played. I thought I hit a good shot into 18, but there was a little mound between me and the pin in the middle of the green. As a result, two putts were only possible if I made a 15-footer, which I didn’t. Not all of the greens were so wild, but many made me look silly. I loved it. It would take a long time to learn how to play the course. I’ve always thought that the greens are what make courses interesting.
White Bear Yacht Club and Crystal Downs are a close second. Finally, some newer courses like Lost Dunes have a lot of slope and undulation. Somehow, they feel different, but I can’t put my finger on why it seems that way.