Here are a selection of great OS X shortcuts:
cmd + shift + 3 – screenshot
cmd + shift + 3 – cropped screenshot
cmd + shift + 3 then press spacebar will crop the screenshot around the current window
ctrl + cmd + space – full emoji keyboard
cmd + ~ – switches between windows in same application
shift + option when changing volume uses quarter increments
cmd + option + shift + V – paste & match text formatting
cmd + space – shows spotlight
cmd + H – hides active application
cmd + opt + H – hides all windows not in focus
alt + backspace – delete a whole word instead of a letter at a time
control + command + power (eject) – system restart
cmd + shift + i (from a Safari or Chrome) – creates a new email with the URL of the page you were visiting in the body
control + d – replicates the ‘Delete’ key from non-mac keyboards
option + right click on a dock app to show force quit
option + click on wifi icon in menu bar to show wireless speed, strength and other useful details
Thanks to reddit.com/r/apple for some of these.