Shia LaBeouf was the guest, but it's Hugo Weaving that's getting the attention from the Allsparkers who saw the Late Show with David Letterman last night.  Weaving's Megatron speaks - rather menacingly, of course; he's Megatron - in the Transformers: Revenge of the Fallen clip that aired during LaBeouf's appearance.  Check out the violently spoilerific clip (well, spoilerific for those who haven't seen the movie yet) on YouTube, and drop by TriBlurr's thread with your comments.