Of all the gift shops in WDW, Japan is among the very best.
It has not changed in a while, but the little museum there is kinda cute. As was already mentioned, there's also a small museum in Norway. There's also a third worthwhile one in Morocco.
If you happen to visit Norway when the creator of the Norway perfume Leila is there, he's really nice. his name is Geir Ness.
The small aquariums in the Seas are worth exploring. They vary and the area can be a bit hit or miss, but the baby tank area had some really interesting critters last month. (though not all of them were babies.)
In the Land, we always look to see what Mickey's Mini Gardens plants they have on sale. They don't seem to live after the jar is opened, but I have had some live for quite a while in the jar. I had a vanilla plant that lived for quite a few years. (You can see the jars in the lab area near the end of the ride).
The world Showcase is really pretty after dark, as is the Boardwalk area outside the back park exit.
If not a sandwich, then a baguette from Les Halles is inexpensive, really good, and just a bit out of the ordinary. They sell out. Also, the Voss water in Norway is worth buying, esp if it is a very hot day. It is the best water!
If you go during one of the holiday periods, they often have a scavenger hunt in the WS. If you want to officially play and get the prize, it costs money, and is a bit overpriced. But you can also just find all the hidden eggs/characters for free.
IMO, the food at the January Art festival is better than the other festivals with shorter lines. the F&W fest used to have a lot of free items long ago. During the spring flower fest, try walking through the butterfly tent/exhibit.
While you are over by the butterfly house, another slightly oddball thing is to use the restrooms that are on the back side of Imagination. They aren't anything crazy, just kinda retro Epcot.
The Moana water attraction is kinda cute, but be sure to take time to try the interactive parts for yourself. Also, at night, take a few minutes to explore the new area by where the Walt statue is. Maybe on your way out of the park.
Get a little free soda in Coke place.