Mine would have to be John Travolta as bad guy... he is so evil... or definately Sean Bean living on a luxury yaught in the waters surrounding the city as an untouchable thug... would have to have Samuel L. Jackson show up as a cameo 'blow some serious **** up' character, and Steve Buscemi as a weird guide / mentor hobo character that keeps showing up randomly. Also, random superheroes flitting in and out of the action would be funny as in GTA (god games would suck if I was lead designer!)