The Ocean Course at Kiawah. Played the Dye tees (6,450 yds.). We played as a twosome, both 7-8 handicaps and both shot mid-90s. As we're coming down 18 bumming out about our scores, the caddy tells us we shouldn't be too disappointed. Most of the people he caddies for don't break 100. Small consolation, but still a memorable experience.
Also, Old Corkscrew in Estero, FL is an under-rated monster. It's a Nicklaus Signature design, open to the public and well worth a visit.
Update - I had the chance to visit The Concession (Bradenton, FL) earlier this year. I was a spectator at The Concession Cup between top amateurs from the US and British Isles (including Ireland). The Concession is always rated as one of the top course in Florida and it deserves the rating. I now refer to Old Corkscrew as the "poor man's Concession." They're both Nicklaus designs and both well east of I-75 (i.e., middle of nowhere), neither has any significant housing in view, and they're both very difficult. Of course, conditioning at The Concession is better.