CS:
Flame Tree BBQ at AK -- not exactly a unique, entertaining atmosphere, but they have a very nice seating area in back, near the water, with a view of Expedition Everest
Boulangerie Patisserie at Epcot -- you can pretend you're in France, lol, but as PPs mentioned, the prices are reasonable and the food is really good.
Cosmic Ray's at MK -- if you're into corny humor, Sonny Eclipse is kind of funny. my kids love him, not so sure if adults would agree
Casey's Corner at MK -- you can sit on the bleachers with your hot dogs and watch cartoons. not an upscale atmosphere, lol, but it's fun if you like that kind of thing (my family does)
TS:
Sci-Fi Dine In at DHS -- for lunch
50's Prime Time Cafe at DHS -- for lunch
The Plaza at MK -- lunch or dinner -- maybe not terribly unique, but it's pretty, like an old fashioned ice cream parlor, with lots of windows and a nice view