Alt+Enter:

Insert a hard return within a cell

Alt+H+D+C:

Delete column

Ctrl+Alt+V:

Open the Paste Special dialog box

Ctrl+C or Ctrl+Insert:

Copy contents of a cell or selected data

Ctrl+V or Shift+Insert:

Paste contents of a cell or selected data

Ctrl+X:

Cut contents of a cell or selected data

Delete:

Remove the contents of a cell or selected data

Enter:

Complete an entry in a cell or the formula bar

Esc:

Cancel an entry in a cell or the formula bar

F2:

Edit a cell

F3:

Paste a cell name (if cells are named in the worksheet)

Shift+F2:

Add or edit a cell comment