When we think of Orson Welles, we usually remember his outstanding work as a director, writer, and producer, as opposed to his actual acting and voice work. But he really was a jack of all Hollywood trades, so to speak - he could do it all. Though he's probably best known for his 1941 film, Citizen Kane, Welles's last major role before his death in 1985 was as the voice of Unicron in Transformers: The Movie.
Famous for films including The Magnificent Ambersons, Touch of Evil, Chimes at Midnight, The Lady from Shanghai, and F for Fake, Welles was highly regarded throughout his entire career. In 2002, he was even voted the greatest director of all time in two British Film Institute polls by his peers. It's hard to imagine him as a transformer, but you can't deny he was diverse!