2. The Tumbler (The Dark Knight Trilogy)
Taking coolness to new levels, having a version of the Batmobile turn in to a Transformer would be fantastic. Imagine, if you will, a Transformer with stealth, speed, heavy armour, heavy weaponry and a whole host of Bat-gadgets to boot. Sweet huh? A jet-black giant robot with the above properties would look amazing and could serve as the Transfomers' Earth-based crime-fighter. It could even bust out the 1960s 'nana-nana-nana-nana... Batman!' theme while it kicked crime's butt. All it needs is a cape, a husky voice and a broody attitude and it will be good to go!
Alignment: Autobot.Potential Transformer name: TumbleBee (sorry, that's REALLY lame).