Mac
Command + A (select all)
Command + B (bold)
Command + C (copy)
Command + Control + F2 (control menu bar with the keyboard)
Command + Control + F3 (control the dock with the keyboard)
Command + End (bottom)
Command + F (find)
Command + F2 (print preview)
Command + F4 (close document)
Command + G (find next)
Command + Home (top)
Command + I (italic font)
Command + M (minimize)
Command + N (new document)
Command + O (open file)
Command + Option + L (spell check)
Command + P (print)
Command + Q (quit)
Command + S (save)
Command + V (paste)
Command + X (cut)
Command + Y (redo)
Command + Z (undo)
PC
ALT + F4 (Close the active item, or quit the active program)
ALT + Tab (Switch between the open items)
CTRL + A (Select all)
CTRL + C (Copy)
CTRL + Down Arrow (Move the insertion point to the beginning of the next paragraph)
CTRL + ESC (Display the Start menu)
CTRL + Left Arrow (Move the insertion point to the beginning of the previous word)
CTRL + Right Arrow (Move the insertion point to the beginning of the next word)
CTRL + Up Arrow (Move the insertion point to the beginning of the previous paragraph)
CTRL + V (Paste)
CTRL + X (Cut)
CTRL + Z (Undo)
F10 key (Activate the menu bar in the active program)
F2 key (Rename the selected item)
F3 key (Search for a file or a folder)
Windows Logo (Display or hide the Start menu)
Windows Logo + D (Display the desktop)
Windows Logo + F (Search for a file or a folder)
Windows Logo + M (Minimize all of the windows)