Mine is a toss-up between "You will be hungry again in an hour.", "That wasn't chicken.", and "Help! I'm trapped in a Chinese fortune cookie factory!"
Admittedly, I've never SEEN any of those in an actual fortune cookie....
Of course, we all know the Fortune Cookie Game: Whatever the dang thing reads, add the words, "...in bed." to the end of it, but I found one that makes that game not work:
"See if you can learn anything from the children."