That's really a subjective question, but to really try and think of it in a un-bias perspective...I'm going to go old school and say....The origianl G1 Optimus Prime. Sure, by todays standards he's kind of a brick(Though what G1 toy isn't.) but look at it this way, he's full alt-mode transforms into a robot, and a play set. You're more or less getting two toys in one. I guess for today you could actually apply this to MP Prime, because I for some reason forgot that there is in fact a trailer set for that...But damn is it pricey though.
