While logged in to a remote ssh session, sometimes I do cat to the wrong file (a binary or a diretory) and the display converts to gibberish. The only way out is to close the terminal and open a new one, which frustrates me because usually there is a lot of state related to the current terminal already.
Update: while I received great answers, a little problem persists. See this follow-up question.
An old trick that works on almost any other Unix type system, too:
That is: Type the word echo than a double quote character then press CTRL and type the kev v then press CTRL and type the key o (the letter not zero) then type another double quote character then press RETURN.
when running screen in your ssh session helps as well, as that one will disable the more uncommon font switching escape sequences (but will of course still work with normal programs). The main reasons for screen are different, usually (switching between programs, disconnecting and getting back to your original programs when reconnecting, etc.)
running reset (or one of the escape combos) works if you ever happen to run into a garbled screen (or a screen that refuses to echo input) again...