Most skills get installed once, used once, and forgotten. This shortlist is the opposite: each item below earned a place because the job it handles comes back, and because the output can be checked rather than taken on faith. A skill you cannot verify is a skill you will stop trusting after the second surprise.
The test an item has to pass
Two uses in a week, on work that mattered, with an output someone else looked at. Anything that fails that test is removed from this list even if we wrote a full editor's note about it. The list changes; the notes stay on the individual pages.
What this list is not
It is not a top-downloads list. Download counts are a popularity signal and nothing more. It is also not a safety endorsement: every item here touches either a document, a repository, or a network path, and each of those needs a scratch scope before you point it at something you cannot restore.
How to use it
Pick one item whose job you did by hand last week. Install it, run it on the smallest version of that job, and compare against what you would have produced. If it saves less than ten minutes, remove it. The pre-install checklist has the full set of questions to ask before you paste the prompt.