1. Jack Nicholson - One Flew Over The Cuckoo's Nest (1975)
No film has ever explored the nature of freedom and conformity in quite so pointed and effective a fashion as Milos Forman's iconic adaptation of Ken Kesey's novel. It's hard to imagine that, once upon a time, Kirk Douglas had his eye on Randle P McMurphy, because Jack Nicholson embodied the part so perfectly that it's pretty much impossible to envisage anyone else in the role. The archetypal tale of a lunatic taking over the asylum, Nicholson's uncouth outsider comes to be the lone voice of reason in the face of an oppressive regime which his fellow inmates choose to live under. It's a wonderful, inspiring display of a spirit which refuses to be broken, an individual who refuses to give up his individuality, and pretty much established Nicholson as the coolest guy around forever. No wonder he's never been seen without sunglasses since. Which movie performance do you think is the most powerful of all time? Share your picks below in the comments thread.