We like Sunshine Seasons at Epcot for QS and Columbia Harbor House at MK.Depends on what you like! I really want to try Satu'li Canteen at AK. And YDS really wants to get the Darth Vader waffles at a QS at HS. (Backlot, I think?)
As far as snacks, we have to get Dole Whips (adults) and Mickey Bars (kids) at least once. I've noticed a lot of the ice cream places have bona fide sundaes for snack credits, and my dad will be all over that. And I can't wait to get something at the caramel place in Germany in Epcot and the ice cream place in France in Epcot.
I'm more about the salty than the sweet, though, so I'm hoping to find a few more snack-y things of that sort. I adore the cheesy pesto bread (snack credit!) at AoA food court.