How many have you seen that were necessary to the plot?

I don't watch GoT, but even someone like me couldn't help but be made aware of the widespread revulsion over what happened in last week's episode. It got me thinking about the question I asked, and these movies immediately came to mind:

The Accused

Irreversible

Rob Roy

A Clockwork Orange

The Shawshank Redemption

Deliverance

...thoughts?