Mark,
When I think of the perfect green, the one that comes to mind is Riviera #10. It is perfectly suited (small size, narrow shape, orientation, tilt and deep frontal bunker protection) to challenge "the specific shot" needed to reach it safely from any location of the approach shot.
On the other hand, none of Oakmont's greens are "small" in size, but likewise, because of their contouring and more laying with the land design, they present very small targets for "the specific shot" demanded for success from any second shot location. In this case "small" is not strictly defined as the square footage of the green.
I know that the "the specific shot" comment will offend some who see that comment as anti-strategic architecture, however, in my opinion, I see it as designing for and demanding the ultimate strategy. The architects took into acount and protected against not one way to play the hole, but every possible way to play the hole.