Imperial Dam

I think when someone says "NPU" it goes beyond just the literal translation of  "nice part use". It's a way of acknowledging another builders ability to see a use or situation for a part that simply had not occurred to you, or most others. Take a look at the waterfall in this brilliant micro castle by Dubbadgrim, that's the ghostly lower half of the ghost figure of series 13 (yes, the back is clear). That's thinking out of the box, and that's NPU.

CCCXIII - Imperial Dam