Notice, the barker isn't really selling the Giant Rat. The Rat is just the means by which to deliver those feelings to the paying crowd. His buyers want to buy emotional stimulation, while he'd be trying to sell them a rat. Obviously the exact words will depend on your product. We're programmed to respond to questions.
People love to learn how to do new things.
We're always fixing something, from a screen door to our body. We especially like to fix our social shortcomings. Many products and services can help buyers feel safer, or more secure. If it won't grab their attention, THEN pull them into the body of your ad, it isn't the right headline. People love to know secrets.