Apparently the conception of the Death Star came from several individuals in Star Wars. This hilarious video from Sneakyzebra shows some characters who claim that the Death Star Was My Idea.
The ad is a spoof of the Windows 7 Was My Idea campaign. In this video, Darth Vader introduces himself casually and starts to recall a memory that gave him inspiration. A reenactment occurs that shows the Sith Lord coming up with plans for the destructive transport as an unlucky individual suffers the wrath of his force. At the end, he reveals that the Death Star Was My Idea.
Don't believe it was Darth Vader? Sneakyzebra also has videos with a Storm Trooper and the fuzzy Chewbacca telling their stories about how they thought of building the destructive ship.