Have you ever wanted to type a Tab character, or a carriage return (line break), into a text field, but it either tabs to the next field, or hits the default button (i.e. "OK"), respectively? A good example is TextEdit's Find dialog. With TextEdit open, type a Tab or Return character into a document, select it, then copy it. Now you can paste your special character into a text field.
The only use I can think of with this is a query (and also replace). You can even do it in the Finder when naming a file/folder, but you get an error. Tab and Return would make good text snippets; I just tested this with Butler, and it worked.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20060829201015323