Interesting question. My mentor dream team would consist of:
I am a combination of interim CFO and mentor / advisor for a bunch of web startups. I have to say that the big names are useless. As an entrepreneur you want someone who is plugged in and gets it, but is not so high profile that they have no time or attention for you. It's tough to find that right person or people. Look for great mentorship potential in your angels. Some of the names listed here are just that - great angels. Then add in paid or unpaid advisors to fill functional gaps, particularly in areas that only kick in after your startup grows (finance being one example)
Without naming specific people some thoughts...
The bigger the name, the more likely the person will be way too busy to be a good mentor. When I asked the question to another entrepreneur, I was advised to work with multiple people and choose those that work the best for you/your company.
The other part here is in not just choosing a good generic mentor, but someone who know your industry well or is an expert in the way you are changing your industry (for example if a SaaS expert if you are trying to bring the accounting world to see the benefits of SaaS).
Chris Sacca, Ron Conway, Jason Calacanis, Tony Hsieh, Jeff Bezos.
Those guys can put a product into orbit and open all the doors you need down the road. Though I chose this list because of each of their track records and expertise. 3 of them have companies and solid track records in my space and two of them could be great CEO coaches and help in the vision brainstorming for next level ideas.
My list of Authors would also inlcude Dale Carnegie.
His writings about communication are a great help for internal and external improvement.
-Peter Norton: Create great products with your talent, then a business.
-Carl Sagan: Communicate complex things and make people wonder about it.
-Vangelis: Develop your style/culture, experiment and innovate.
-Rober Rodriguez: Maximize minimum resources with creativity.
-George Patton: Design and perform brilliant strategies in adverse scenarios.
-Hayman Rickover: Manage an organization to deal with a very complex matter.
Why not to choose an ideal team of co-workers for your business instead of asking for mentorship some people you are not acquainted with?
If you dig deeper you'll find that some of them are not 'dream' members at all. For example, Napoleon Hill left some bankrupt businesses after him and nothing else.
I know, it's dream team so I'm allowed to put in fictional ones too ;)