An ad for the game Daikatana that Ion Storm later came to regret greatly. If memory serves me correctly then the ad featured a red background with the words "John Romero is going to make you his bitch" in very large black ink, below it, and in parenthesis it had the words "Suck it down."
Understandably, many people were offended by the ad, not for the content, but for the sheer pretentiousness of it. Especially when the game didn't come out for another three years or so after.
If the man who wrote the Salon article is to be believed, it was meant as a sort of joke on how people talk during a deathmatch.
An ad that for a normal game would have been a humiliating moment, instead became a footnote in gaming history due to the game sucking horrendously.
As a random factoid Master Villain mentioned that "suck it down" was a sort of personal catchphrase of John Romero.
Update March 12 2004: A scan of the ad can be found on Gamespot at the following URL: