I discovered the goddamn \G trick about six months ago. I couldn't believe I hadn't picked it up anywhere else. It's the most useful thing you can learn when dealing with the MySQL shell! (Especially when your eyes buzz out trying to line up a huge table!)
clear (\c) Clear command.
edit (\e) Edit command with $EDITOR.
ego (\G) Send command to mysql server, display result vertically.
quit (\q) Quit mysql.
source (\.) Execute an SQL script file. Takes a file name as an argument.
system (\!) Execute a system shell command.
tee (\T) Set outfile [to_outfile]. Append everything into given outfile.
\c alone could save you a ton of headache. \e's pretty classy, too; just make sure you follow it with a semicolon to execute the command.