When Guy Laliberté, founder of the Cirque Du Soleil, met with the remaining Beatles to pitch the concept of 'Love' - a show that would integrate their songs in a most creative format - he used only three words. After years of trying to get his idea through, now sitting in front of them, he had the chance of the lifetime to convince them. The normal reaction would have been to elaborate fantastic concepts to wow The Beatles. But he just used three words that were powerful enough to move them:

Let's have fun.

The Fun Theory is a web site that tries to get ordinary people change habits by making the alternative habit a fun one. Here is an example of getting people to use the stairs instead of the escalator.

Fun. It's the unique value proposition.