Guess the price of an item for a huge discount!! Can be used by ecommerce companies and tweaked to use for other types of companies..ex. pizza shop coming out with a new topping can have the user guess the topping for a free pizza..
This helps the business see what the user would want the price of the item to be (or the toppign of the pizza) which gives more consumer knowledge so the business can adapt to the user. It also is fun for the customer and brings traffic to the site.