The idea of a Cybertronian alternate mode doesn’t seem to go well with some people, who feel that the alt mode should serve only as a disguise for the robot (truck, car, tank, etc). But I think the way it works is that some Transformers are able to change form not just to adapt to a new world, but to also provide some sort of function. For instance, Bay07/PRIME Megatron can transform into a Cybertronian jet, which is hardly a disguise but does allow him the function of flight; it also marks him and any other Decepticon out as a purist – no impure Earth disguises, nothing but Cybertronian alt modes, that sort of thing. My vote goes to Soundwave. I liked Megatron’s alternate modes, but the satellite was just so fitting for Soundwave, and had an awesome design too (wings, panels, compartments, and of course the tentacles). On a side note, if they feature a purely Cybertronian alt mode again it should be Blitzwing– no Earth tank or jet can be feasibly stuck together on a Transformer, so I guess they might as well make it him.