You may have seen
Sorry to disappoint folks, but there aren't actually many hidden units that are cheat units. Typically you can get these by typing in a cheat while in-game to create the unit for various sorts of AI destruction.
Extra rubble piles even though three of them are the same as Rubble 1x1, Rubble 2x2 and Rubble 3x3. Will disappear in the editor if a different PILE # is placed overlapping or too close to another.
Ok so this is what this thread is really all about, we'll run through the ones mentioned in the previous article but we'll also talk about some others.