DreamWorks LLC / Paramount
BASE MODEL: Part-time cab-over semi, part-time robot leader of the peace-loving Autobots of Cybertron, Optimus Prime was the good face of "Transformers" through multiple comic book and TV series. His trailer detached and became the Autobots' command deck, and his death in "Transformers: The Movie" taught a lot of grade schoolers some hard facts about life.
UPDATE: Michael Bay's 2007 big-screen interpretation of the long-running franchise expanded the role of humans in the Transformers universe, making their speech capabilities seem even stranger in contrast. But luckily, original Prime voice actor Peter Cullen reprised his role.
UPGRADE: For the movie, Prime ditched his transforming trailer, but retained the little-seen energon power ax he used only once in the original animated series.