MK: Columbia Harbour House...the sandwhiches are great!
Epcot: Kringla Bakeri og Kafe has great smoked salmon and the best desserts. Mmm...school bread...
DHS: Pizza Planet is always pretty good. I would also recommend a cuban sandwhich from ABC Commisary
AK: Flame Tree Barbeque has large portions, good food, and great outdoor seating (on the waterfront)
DTD: The Earl of Sandwhich has wonderful hot sandwhiches.