PowerToys is Microsoft's open-source collection of Windows efficiency tools, modular so you enable what you want, on Windows 10/11.
A few I use often: Alt + Space opens a launcher to search files, open web pages, do quick math; double-tap Ctrl finds the mouse; select a file and press Space to preview it; Win + Shift + T extracts text; Win + Ctrl + T keeps the active window always on top.