SystemHack is a project from Croatia's Multimedia Institute — a book and website that documents great and seminal hacks through time. The site for the project invites you to submit your own favorite hacks to the list:
A moment of excellence in programming is called hack. A perfect hack is surprising, mediagenic, lucid in employing technology, funny and non-violent. System.hack is every hack that opens up a closed system or makes an open system continually dynamic.
What are your favourite System.hacks ever?
(Thanks, Tom!)