3. KFC's Fried Chicken
Every fast food ad promises a special sauce or the best burger in the business, but when it comes to secret recipes, KFC (YUM) has the lock -- literally. The company's still uses Colonel Sanders' original, hand-written list of eleven herbs and spices, and its security precautions put the Pentagon to shame. In 2008, when the company updated its headquarters, it gave reporters a glimpse behind the curtain. The ingredient list is kept in a computerized vault with two separate locks, alongside vials of the eleven seasonings, and only two executives have access to the full recipe. By comparison, when McDonald's (MCD) substituted a cheaper version of its classic Big Mac "special sauce" in the 1980's, it lost the original recipe, only finding it in 2004, when it decided to switch back to the original.
(AP Images/Michael Dwyer)