I love this video from Tufts University. It show a couple of students from the EN10 subject showing off the spelling game they build for kids.
From what I can tell, each block has a particular colour, and in each slot is a light/colour sensor. The NXT reads in the combination, figures out if it is a valid word (lookup table??). If it is a real word, the little leprechaun moves along the rainbow.
What makes the video for me is the enthusiasm of the (university level) students for a spelling game. Oh, and the green hats :)
Video is embedded from Facebook, so not sure if it'll work.
Direct link here - https://www.facebook.com/video/video.php?v=180530342035361