6. Blood Meridian
Cormac McCarthy's magnum opus Blood Meridian was first published in 1985, and even though the critical consensus has changed over the years, it's consistently been dubbed unfilmable. It is ostensibly a Western, but it's horrifically violent and filled with characters who would pose a challenge to any casting agent. This hasn't stopped a number of directors stepping up to helm a film adaptation in the last few years without success. Ridley Scott expressed an interest in Blood Meridian back in 2008, with Bill Monahan of The Departed working on the script, but both eventually moved on. Scott passed the buck to Todd Field, whose involvement also seems to have come to an end. Most recently, James Franco went as far as filming test footage in 2010 to prove he could direct the adaptation, but that's also fizzled out. Perhaps it's for the best, as Scott admitted that studios were a little resistant in the first place.