I like to think I make a pretty good 404 page. Not a lot of people see them, so I thought I'd document a few from Co-Opp over the past few years.
2008: This was the first 404 page I developed for Co-Opp. At the time, the Co-Opp logo was sitting on top of a bunch of blue circles with some drips coming off the bottom. I decided to spin that familiar vision of the logo slightly and have the blue cloud turn in to a pool of blood.
2009: The logo changed slightly when the website was redesigned in 2009 and the logo no longer sat on a cloud of blue drippiness. As such the previous 404's pun was no longer relevant. Although still a good 404 page, I wanted something new and something more related to classic gaming that the logo represented. I came up with the idea of using the 404 to represent a classic game over screen.
2011: In early 2011, Co-Opp experienced a complete shift. The logo was back to the original one and everything became much more refined in purpose. I thought for a few days what I would use for a 404 page. I was very close to setting up a scene in Team Fortress 2 (via Garry's Mod) of a battle and having the Co-Opp logo lay dead in the middle saying something like, "Oh no! The page you were looking for was killed in cross-fire!" or something. A member of Co-Opp posted a photo to his Facebook account showing him ferociously about to eat a bunch of peas, and everything just clicked.