Clara's hat in The Light in the Piazza. Simple, beautiful, and touching. It doesn't matter if you know it's coming or you see the string, it still has a lasting effect. Wonderful storytelling.
Did anyone else see the RSC's 'Tempest' this season? Because when Ariel came out of that seal... WOAH. "Ariel appears to the three "men of sin" as a harpy, reprimanding them for their betrayal of Prospero" is how the scene is described on the Wikipedia. It's really hard to describe, but if you can imagine someone who is half Disney's Hades and half skeletal bat unexpectedly rising, covered in blood, out of a seal carcass, then you've pretty much got the idea of the scene. I don't remember anything else impressing me quite so much. I guess it was the excellent combination of the unexpected occurrence and the disturbing costume. ^_^
Although whoever said the transition into 'No Good Deed' in 'Wicked'? I'm with ya there! 'No Good Deed' is my favourite scene in the show; I nearly hyperventilated the first time I saw it, because I found the whole thing so powerful. Mock if you will, but it's true. ^_^
I am so glad you have that picture, my description was so wordy and silly. XD But yes! Having THAT appear onstage when you least expect it is just plain amazing!