Denzel instead of Pitt?
I know that initially they wanted Denzel to be Mills and that Pitt was maybe better in terms of playing hot-shot cocky young guy but just imagining Denzel + Freeman in a movie like Se7en? Nah.. That would be too much badass. The universe would explode
Update:
Imagine a bald Denzel playing John Doe. :D Movies like Man on Fire totally proved that he can be a John Doe