So I guess that this would be World War Hulk versus the Ultron from Ultron Unlimited (The one that destroyed a country.). I remember Ultron and the Hulk having an encounter during Secret Wars. I forgot exactly what happened, but I don't think that it was that much of a fight. Ultron did take on a few heroes at the same time though, and he is able to take on the entire team of the Avengers on a regular basis (And I think that he took on the Fantastic Four as well.). I think that regular Ultron can beat the regular version of the Hulk, but I don't think that he can beat World War Hulk. Then again, Ultron can't be permanently destroyed can he?
What about Magneto and Ultron? Have these two ever fought? I think that this would be a cool fight. Now we know that Mags can pull out Wolverine's adamantium, but isn't Ultron's a lot tougher? Somehow I see Ultron taking precautions. What do you guys think?