Optimus Prime is the leader of the Autobots and one of the coolest robots ever. Optimus is badass for a couple of reasons; First, he's a giant frikkin alien robot with a huge laser gun and superhuman leadership, managerial and networking skills. Second, he can turn into a goddamned Mack Truck and run over anything that crosses him. Like any good comic book/cartoon character, he sacrificed his life to save his teammates, only to be revived later and take over his position as leader of his organization as if nothing had happened. In this sense, he's the Christ-like figure of the 80's children's cartoon era. How's that for symbolism, Mrs. Fernandes, you miserable wretch?
Prime has been in charge of his crack team of alien robots that turn into cars for, I think like a thousand years, and he continues to inspire nostalgia into the hearts of anyone who ever followed the Transformers. On top of that, he's easily the toughest and most badass robot-alien-motor vehicle among his people, and since he's just a robot he can't ever really be killed because they can just rebuild him. Plus he gets bonus points for avenging his own death. Not a lot of people can claim that they've accomplished that.