We have over 6000 mentors, so this is a very hard question to answer. You can see your local mentors by going to http://fi.co/mentors. New mentors are added frequently.
Many mentors also have local experience launching startups. For example, our best mentor in Silicon Valley, will not typically be an expert at launching a business in Singapore.
Our most experienced mentor in launching startups globally would probably be our CEO, Adeo Ressi.