Transformers is an awesome movie, partly because of the prolific robot violence, but also because of the cool sound effects.  Hearing that wahnt-wahnt-wahnt-wahnt-wahnt takes me right back to 1989, sitting on my neighbor's couch on weekday afternoons, preceded by G.I. Joe and other amazing cartoons.  I just learned that the voice of Optimus Prime is actually the voice of a human named Peter Cullen.  I always thought it was some sort of electronic effect.  But like Hal Douglas and Don LaFontaine, he's just a guy with a cool recognizable voice. 

On a related note, there's an adult-sized Transformers helmet that electronically alters your voice when you speak through the microphone.  It doesn't sound much like Optimus Prime, but it's mildly close. #entertainment