Ask HN: Best quick references/cheat sheets?

I went to a friend's place and he had two pieces of paper taped to the wall next to his desk: the visual studio code keyboard shortcuts cheat sheet ( https://code.visualstudio.com/shortcuts/keyboard-shortcuts-windows.pdf ) and the atlassian git cheat sheet ( https://www.atlassian.com/dam/jcr:e7e22f25-bba2-4ef1-a197-53f46b6df4a5/SWTM-2088_Atlassian-Git-Cheatsheet.pdf ) do you have anything like this that you reference a lot? I feel dumb for not having thought of this before. Anything like this you use regularly? regardless of language ,tool, framework, etc