You're in luck. Just head over to http://www.wheelofconcept.com/
It's called the Wheel of Concept, from Tribal DBD New York. Just enter your client's name, spin the wheel, and up pops an idea. Even better, you can download a PDF presentation of the idea, personalized with your client's name and logo.
Actually, there are now two wheels: the original for digital tactics and a recently added one for PR tactics.