David Kaye interview
He played (the second) Megatron (he named himself after the original one we knew in 1984, 1985, and s on). on Beast Wars Transformers and Beast Machines Transformers.
He then played a different character named Megatron on Transformers Armada, Transformers Energon and Transformers Cybertron.
He was the voice of Professor X, Professor Charles Xavier on that terrible X-Men Evolution program.
He currently is the voice of Optimus Prime on Transformers: Animated.