Lojban
Permanent link to this comic: http://xkcd.com/191/
Image URL (for hotlinking/embedding): http://imgs.xkcd.com/comics/lojban.png
Man: If you learned to speak Lojban, your communication would be completely unambiguous and logical.
Man in black hat: Yeah, but it would all be with the kind of people who learn Lojban.