3M was so sure their Security Glass was unbreakable, they put a large stack of cash behind it and shoved it in a bus stop. Great advertisement, right?
Actually, it was only $500 of real currency stacked on top of fake money, and people could only use their feet to try to break it. A security guard was present to make sure no one broke the rules and that people couldn't get to keep the money if they broke it.
Nevertheless, a glass that can stand a double-footed kick from a man with a 30 foot head start is impressive. Don't you wish your iPod screens were made out of this?
3M Security Glass Ad [37 Signals]