Before you answer the question as to why you would want to join Accenture, first find out as much as you can about the company. According to their website, most employees tend to find their way to the company because of the kind of work they do.
The company feels strongly about their contribution to shaping government, business and society. Furthermore, the company feels strongly about its responsibility towards its clients and its community.
Accenture puts a lot of value in high performers that enjoy the working environment they have created.
These are really good buzzwords to be used in your application because they will show that you are compatible with what they are searching for in an employee.
Basically, what it comes down to is that the company is looking to hire employees who will thrive in the environment they have created.
If you want to ensure you get a chance at an interview, you need to make sure you know the company well enough to show them you will do well.
Good luck!