Being just a LaTeX user, I have to look up documentation very often. What could be easier than
texdoc packagename and here it is.
The other day I opened for curiosity the
scontents package and was taken aback how -- how to express that in English? -- »intricate« the manual had been typeset.
The beautifully typeset documentations may serve as good use cases for people in search of inspiration.
So I'm asking you to say which package documentation you found outstanding in design and typesetting.