File > Revert… (Mathematica Menu Item)

Revert restores the current notebook to its last saved version.

Insert > Special Character… (Mathematica Menu Item)

Special Character opens the Special Characters palette.

Insert > Table/Matrix > Split Spanning (Mathematica Menu Item)

Split Spanning divides a spanning entry from a formatted grid into separate entries.

Window > Tile Windows Tall (Mathematica Menu Item)

Tile Windows Tall arranges all windows to fit in the screen one beside the other (Windows and Macintosh only).

Window > Tile Windows Wide (Mathematica Menu Item)

Tile Windows Wide arranges all windows to fit in the screen one above the other (Windows and Macintosh only).

Help > Virtual Book (Mathematica Menu Item)

Virtual Book opens the Wolfram Mathematica Virtual Book, an updated and expanded electronic version of The Mathematica Book.

Help > Welcome Screen... (Mathematica Menu Item)

Welcome Screen opens the Welcome Screen, which appears by default each time you start Mathematica.

Wrap at Paper Width wraps lines at the width of the paper currently specified by the print settings.

Format > Word Wrapping >  Wrap at ... (Mathematica Menu Item)

Wrap at Window Width wraps lines at the width of the window containing the text.

AbsoluteFileName (Built-in Mathematica Symbol)

AbsoluteFileName["name"] gives the full absolute version of the name for a file in your filesystem.