Prime. The Peterbilt looks very heroic and imposing. In fact, every time I see a Peterbilt (regardless of model), I always think of Optimus.
Ironhide! That truck is just one sexy beast! OP looks pretty damn good too. BB, well my jaw hit the floor when I first saw him, and Jazz is just sexy all around. But that truck fit Ironhide perfectly! A badass truck for a badass bot! I must say Mr. Bay did good with this one.
All of 'em, I think each vehicle choice was perfect and equally badass for each character. Even Ratchet, the medic, looked like he could go rounds with a the likes of Ironhide with his roll cage parts, giant wheels and the like. Ironhide's Movie Alt Mode should be the default for all future incarnations. Well, Movie Ironhide should just be the default for all future incarnations.
First, I was gonna just vote for BB, because TF1 Camaro started my love for the cars. Then, decided to vote Ironhide also, because he's a Topkick and it look absolutely epic. Next, I wanted to vote for Jazz too, because every time I see a Solstice, I get excited and think of Jazz. Finally, I just said 'screw it, I'll vote for 'em all because I love each one so much!'