Favorite movie where a character goes crazy.

I would reply, but it was a joke meant for the politics section.

I saw a movie with Tim Robbins last month called "Noise" (2007). Tim Robbins lives in New York and he is driven mad by all the street noise and takes matter into his own hands. It wasn't a great movie but it was interesting.

The Aviator (2004) not a favorite but a good example of the subject matter.

Psycho

I like Daisy (Brittany Murphy) in Girl, Interrupted (1999). I prefer the subtlety of her descent, rather than big, predictable Jack Nicholson type madness.