This is similar to the Marvel casting thread except now with the Ultimate Universe. I know what you're thinking, that a lot of the casting would be the same, but I believe that there are actors more suited for the Ultimate verse than the 616 verse and also there being characters that are entirely new or just radically different form their 616 counterparts that the same person couldn't play in both universes.
So anyways, what celebrities would you cast in what roles in the Ultimate Universe? It's simple, just post a pic of the celebrity alongside a pic of the character you want them to play. I'll go first:
as Gregory Stark:
As soon as I first saw Gregory in Ultimate Avengers 1, I immediately thought Daniel Craig would be great to play him. Millar probably already had him in mind when he wrote him which is the same way Nick Fury looks like Samuel Jackson.