Bwahaha! Sometimes people have the funniest things as warning labels on products.
Either stating the really obvious, for people who are, I suppose, even more stupid than you'd expect, or forbidding seemingly strange uses of the product that someone, somewhere, actually made (think "dry cat in microwave"). Some are simply funny because they were apparently translated from Japanese into English by an Armenian, or something like that.
Here's the list, and here are a couple favourites:
"Do not recharge, put in backwards, or use." -- On a battery.
"Do not look into laser with remaining eye." -- On a laser pointer.
"Warning: has been found to cause cancer in laboratory mice." -- On a box of rat poison.
"Warning: May cause drowsiness." -- On a bottle of Nytol, a brand of sleeping pills.
"Remove wrapper, open mouth, insert muffin, eat." -- Instructions on the packaging for a muffin at a 7-11.
"Do not turn upside down." -- </i>On the bottom of a supermarket dessert box.</i>
Edit: you may also be interested in the main "Things People Said" page.