Loads of shortcuts:
F2: rename
F3: find
Alt F4: close window, ctrl-w seems to do this a lot these days too
Alt minus: show child document window menu
Alt space: show window menu, useful if you remember the X for maximize/minimize, z for resize, m for move, r for restore immediately afterwards.
F4 go to address bar in Explorer
F5 refresh
Ctrl F6 switch windows in MDI interface
Ctrl escape: show start menu
Shift-F10: right click menu
Windows E: explorer
Alt-up in explorer: go to directory above; backspace/alt-left: go to previous history item
Windows W windows ink for annotation
Windows R for run
Windows U for narrator
Windows F used to do find but now shows the feedback tool, which I think is a loss
Any command after the word control will open control panel to the right place, eg control display
Windows D show desktop toggle
Windows M minimise all windows, windows shift M restore windows
Ctrl-shift-escape: show task manager
Ctrl tab/ctrl-shift-tab move to next/previous UI item so you can use the UI with a keyboard; this is why web apps that pretend to be native are so useless and annoying because this doesn't work
Also system items normally end with .msc to open the management console, eg. Compmgmt.msc. There's a load of these that help you get to the nitty gritty of the system.
Turn on "show accelerators" in accessibility and menu entries and buttons will have their accelerator underlined, eg the O in OK or F in File. You can then use alt-(letter) to go to it, eg alt-f to open the file menu, s for save.
Honestly I don't know how I would have got through using Windows for decades without these shortcuts. I always find the Mac relies on mouse usage a lot more and the ctrl-F2 and ctrl-F3 shortcut to get to the menu bar and dock on Mac doesn't compare.