I recently spent a couple of months in Bristol, whereby I was invited to watch a few episodes of Misfits. I grew fascinated by the character Simon Bellamy, whose eyes told the story of somebody struggling to fit into society; The intensity in the eyes, coupled with nervous eye darts that looked within the mind of the character. I found a few frames that illustrated this point. The first one shows illustrates a stunned sadness, through this intense focus. His thoughts are slower, but plenty still happens in the eye movements while the pupils maintain an intensity. Please note, by intensity, I mean you would look for an opportunity to show much more white around the pupil.
Next I like how a nervous smile, is partnered with this intense look. It has a disturbing quality to it.
A more well known character is Gollum from Peter Jackson's Lord of the Rings. I love how Gollum's insecurities are illustrated by his inability to meet the gaze of his other self. Simon feels more of a threat, due to the lack of blinks. Similar to the characters Kirsten Stewart plays, Gollum blinks a lot. He is a more animated character in terms of his hyperactive energy levels.