Alt-tab

One shortcut I use all the time is Alt-Tab to switch between windows.

Source: tatoeba (10044976)

If I Alt-Tabbed through all other open programs, eventually returning to the screen from which the cursor disappeared, it would reappear and everything seemed fine.

Source: wiktionary

‘Oh, good,’ said Professor Wright brightly, Alt'''-tabbing to her calendar and skimming the appointment.

Source: wiktionary

At times when I was deep in the middle of a calculation, that sudden shudder of my chair and his shrill voice pulled me out of my semi-trance state as I alt-tabbed to hide any confidential data and turned my chair around to entertain his novel question.

Source: wiktionary