Watson winning $1 million on Jeopardy has to be one of the most remarkable marketing campaigns in tech history. I don't think they get enough credit for it. Every time I hear about IBM's Watson, the story is always prefaced with this Jeopardy event, which must be a huge help when getting business contracts. I think it's absolutely brilliant.
This is a great example of what Paul Graham calls a "submarine", (I think nowadays the common term is "content marketing"?).