Mac Must-Know Keyboard Shortcuts

For my own reference
Collection of Mac keyboard shortcut. The list will go on...

Cmd+C - Copy
Cmd+Opt+V - Paste
Shift+Cmd+4 - Print Screen and save to desktop
Shift+Ctrl+Cmd+4 - Print Screen and save to clipboard (no image will save to your desktop)
Hold cmd+RightClick Trash - Securely empty trash