My personal favorites:
Boathouse - dockside bar it possible. If that's busy, try to get an outside seat at the Hangar Bar next door. Both overlook the amphicar launch and the water. Great sunsets.
Raglan Road - just because.
Morimoto Asia - sushi bar or the main ribbon bar inside. They also have outdoor seating overlooking the 'spring' of DS.
I've heard good things about Paddlefish and Wine Bar George, those are on the list if we get back this fall for food & wine. And Mo has a permanent seat at Dockside Margaritas.
Geyser Point - hands down my favorite outside bar/casual dining.
California Grill bar area - solid #2
Tiki Terrace at the Poly - great for afternoons, if the weather is gross you can go check out the Kona Cafe or the bar outside 'oHana.
Hurricane Hannah's at the Y&B club or the Big River Grille if you're over by EPCOT.
Animal Kingdom: Nomad Lounge.
EPCOT: We really don't have a favorite there for a quick dining option, other than to grab a beer and some fish & chips from the cart outside the Rose & Crown and watch the band play in the garden at the UK Pavilion.
Hollywood Studios: The Baseline tap house, or if you want a meal instead of appetizers hit up the Tune In Lounge at the 50's prime time diner or the outside bar area next to the Hollywood Brown Derby. Both have a slightly modified menu of the restaurants they are attached to.
MK: Skipper Canteen, you can usually get a walk up reservation there. The dining options at MK are pretty limited, honestly.
Where are you staying?