MK--Columbia Harbor House and Cosmic Ray's. I love the tuna salad sandwich at CHH. It's light and refreshing on a hot day and always has fresh, thick tomato slices. The chicken and rib combo at Cosmic's is as good or better than some table service meals we've had in WDW.
Epcot--I don't think we've ever had a bad meal in Epcot, counter or table service. We love the food at Sunshine Seasons and the air conditioning there as well as their dessert counter. And as mentioned by PPs, the CS in Morocco is truly outstanding.
AK--I really like the hot Italian sandwich at Pizzafari. It came with a refreshing side Caesar salad last summer. Haven't tried Flame Tree or Yak & Yeti because I have a bird phobia and can't deal with them trying to attack my food.
DHS--Haven't found any CS that's been exceptional. We do enjoy the Sci-Fi restaurant though.