Madonna turned down the role of Nomi in Showgirls.
The main role was offered to A-listers like Drew Barrymore, Sharon Stone, and most notably, Madonna. She was actually interested, but only if major changes were made to the NC-17 film. The filmmakers refused, so Madonna passed, and they went with Elizabeth Berkley. The film ended up becoming a flop, but also a cult classic.
In Will Smith's case for example, if someone just described the concept for " Wild, wild west", it sounds pretty amazing. While you could easily interpret "The Matrix" as: "sounds a bit crazy and out there".
I’m sick of him almost being in every movie.