If you pre-order War for Cybertron from a Gamestop store, you get a code which unlocks Shockwave in the game. This we know.

However, if you pre-order the game from Amazon, you get a code for...Demolisher?

Yes, Armada Demolisher is in War for Cybertron, albeit redesigned with the game's aesthetic in mind. I think he looks cool. The unfortunate thing is that these codes are only for the Xbox 360 and PS3 versions of WfC, although considering how the pre-order content for the RotF game was actually unlockable in the game without the special code, they might just be hidden characters in the other versions.