Random shell commands

!!              Last command  
!^              First argument word of last command  
!$              Last word of last command  
!*              All arguments of last command  
!n              Command n  
!-n             nth command from the last  
!str            Last command starting with str  
!?str?          Last command containing str  
^str1^str2      Substitute str2 for str1 in last command. (Used only at the beginning of a line.)  

;
 Semicolon
 A semicolon is used to separate two commands on one line.
 
&
 Ampersand
 Run the previous command in the background.
 
&&
 Double Ampersand
 Run the comand following this only if the previous command completes successfully.
 
||
 Double Pipe
 Run the comand following this only if the previous command did not complete successfully.
 
( )
 Parentheses
 The command within the parentheses is executed in a sub-shell.
 
' '
 Forward Single Quotes
 Don't allow any special meaning to any characters within these quotations. 
 
' '
 Double Quotes
 Allow variable and command substitutions within these quotes. 
 
`command`
 Back Quotes
 Take the output of the command inside the back quotes and substitute it as an argument on the command line.
 
\
 Backslash
 Take the following character literally. Also used to "escape" a new-line character so you can continue a 
 command on more than one line. 

echo Ctrl+V Ctrl+O     		restores a screwed up terminal, the Ctrl+O resets text attributes and
                                character set, the Ctrl+V is just to mask the O