The guy who published a book about XSS, which ended up causing an XSS exploit on Amazon via the "book preview" function[1] is my favorite version of that.

There was also an attempted attack on the Swedish voting system via a handwritten SQL injection attack, but that was unsuccessful[2].

[1] https://drwetter.eu/amazon/storedXSS-vuln.at.amazon.html

[2] http://alicebobandmallory.com/articles/2010/09/23/did-little...