Also, ctrl is the hack workaround for the infamous one-button mouse.
Win+x, u u to quickly shutdown Windows. Although I've done this lots of times and not realised Notepad was open and my laptop has been on in my bag all night (my work one stays on when the lid is closed).
Not a keyboard shortcut but you can customise Explorer so it defaults to starting at This PC.
Winkey+D to minimise all windows, then Winkey+D to restore them all.
Winkey+L to quickly lock my work machine
Alt+S to send an email in Outlook.
Found this useful whilst currently working from home over a laggy RDP connection to my work desktop PC, where every mouse move is slow. The less mouse the better.
Ctrl-Shift-Delete
Clear recent history (cache preselected). Maybe not my "favourite" since I only discovered it yesterday while doing frequent updates of cached JSON bits.