I know it sounds silly, and is not a "how did they do that?" type of effect, but the fiber optic lights in the sidewalk at Epcot at night, is my can't miss effect. It makes me so ridiculously happy, and I can't explain why. I love anything with fiber optic lights because of my memories of when I was a child in Epcot. (I used to be obsessed with those fiber optic strand "wands" we had during fireworks).
I'm also excited to see the new interactive queue for Peter Pan for the first time. From the
youtube videos I've watched, that looks like it'll be a can't miss for me too.