The more I play St. Martins the more I enjoy it. It's rarely discussed, and drastically overshadowed by the other PCC courses, but is fantastic jewel of a course. I can imagine being a kid again and having nearly free reign on that course all summer long. Unfortunately a fun as it is, and perfectly suited for hickory play, it does not have the teeth to compete with the other great 9 holers.
Sweetens and Suwanee are fantastic Tennessee cousins, as similar and as different as possible. From tee to green Suwanee is a more demanding course, but that all changes when it comes to the greens. The quality of design and play-ability of the greens around Sweetens is what makes the golf course so special. At times the pin positions demand you to truly plan out your approach, at others your goal is to just feed the ball towards a certain sector of the green and let gravity do the rest. I could see the possibility of playing consecutive 9's there and having an 8-10 shot swing between 9's just because of the greens. Where as Suwanee is predictable, Sweetens can be just simply humbling, but in a way that brings you back every time.
One of my all time favorites is the cow pasture course in Atlanta known as Candler Park. At about $1 per hole for city residence its about as cheap as you can find for golf, and at times you get what you pay for. but there is so much quirk and charm on those few acres of fairway.