Depends on your definition of "famous." If it could be anyone of modest popularity whom I've never met, I'd go with Jimmy "the Rev" Sullivan, drummer from Avenged Sevenfold. He is by far the most influencial person I've never met on my life as a whole, he was arguably one of this generation's top drum talents, and he was always making people laugh and enjoy themselves wherever he went. Not even a debate, for me. Although if we define this as "everyone knows this guy/girl famous," then Nikola Tesla is definitely someone who'd make things interesting.