Spoiler Alert. On the next page you'll see video of the location of the Guybrush Threepwood costume holocron in Star Wars: The Force Unleashed II. You'll also get detailed instructions on finding it, and see Threepkiller in action.
In this video, Kotaku reader Matt B. has already unlocked the costume, so the holocron no longer appears. But he points out its location and recreates what you have to do to find it. According to the instructions, the game is so obviously pointing out this secret location that it's likely many will happen across it naturally. So if you want to be surprised, just click back on your browser. The instructions and video are below.
This can be done just after smashing a frozen door towards the end of level 2. You come into a room with three Guybrush statues all looking at a Jabba The Hut hologram. Stand on the platform of the hologram and you will hear The Monkey Island Theme playing. Force push all the items in the room and a Red Holocron Costume will appear. Collect it to unlock.