For $10 and under you are talking counter service.
I'll second Columbia Harbour House at MK, esp the tuna sandwich!
At Tusker House in AK, you can get a large hunk of salmon with rice and vegetable for $8, an excellent deal.
In Epcot, Sunshine Seasons in the Land pavilion has recently been remodeled and has a lot of interesting variety. Also Tangierine Cafe (Morocco) has had a lot of good reviews.
In DTD, you can get TWO great sandwiches at Earl of Sandwich for $10! Large but not huge, and really yummy!
Several of the deluxe resorts have "food stand" places where you can grab a bite or a simple meal, including Mara at AKL, Captain Cooks at the Polynesian, Roaring Forks at WL, Beach Club Marketplace (guess where?), and Picabu (formerly Tubbi's) at the Dolphin.