Ask YC: What is the Web's Best BUZZZZ MARKETING?

DreamIT Ventures has Mark Hughes speak, the guy who literally wrote the book on Buzz Marketing. Mark put Half.com on the map (literally) by purchasing a town and changing it's name to Half.com. His team also was responsible for the Urinal Screen Advertising Campaign that got them incredible exposure (http://tapinko.com/uploaded_images/Photo-45-797908.jpg). This experience has influenced me to ask the question:

What have been the best Buzz Marketing campaigns?