That's nothing, the President of Bolivia came over for dinner!
Seriously, he was visiting my department in grad school and my housemate, who's also in the same department, was asking him some questions, and after she finished he said okay now I have a question for you -- what is there to do here that's fun, because my evening is free. And she invited him over for dinner! And so he, his wife, and his bodyguards all came over! With an hour of time to prepare and nothing in the house to serve (uh, pasta, Mr. President? 😉 ).
Edit: I've also met (on the "in the same large room as" level, not personally): Tony Blair, Paul Martin, the majority of the Democratic contenders to run for president last time i.e. before they picked Kerry & Edwards, the President of Botswana, the President of Pakistan, a former President of Brazil, and... a few others I forget right now -- oh, and don't forget, Terry Pratchett! (No joke!)