Blomkamp initially approached Ninja of Die Antwoord to play the lead in Elysium. Ninja didn't want his first screen role to be an American-accented character in such a high-profile film.
Blomkamp subsequently approached Eminem, who was interested—but only if the shoot took place in his hometown of Detroit. [source]
[checks to see if this is a joke or not]
Huh. Not a joke. Dude really wanted to cast a white rapper.
I think Slug (Atmosphere) would've worked.