Quarterly Fundraiser Nothing earthshaking. My inclination, given advance notice, would be to try to familiarize myself with the guest philosopher's work and ask about something I found interesting. For example, I asked Chalmers about a couple of variations of his neural-silicon-replacement thought experiments. I'd still ask him about one; he proposes replacing a person's neurons with functionally equivalent chips one-by-one, and if by the end of the process the person still reports no change, this would make a strong case for organizational invariance. I'm not convinced that this would establish what he thinks it would.
Dennett would be a thrill for me too. If I had the opportunity to ask him something right now off the top of my head, I'd ask him why he equivocates on the word "seems" in his "Quining Qualia" paper, or so it seems to me at least.
:) Given time, though, I'd try to familiarize myself with more recent work of his.
But I'd love the opportunity to ask questions of many others too, if I had time to prepare -- Strawson, Searle, Nagel, Bostrom, McGinn, Max Tegmark (not really a philosopher per se) come to mind, others escape me at the moment.