Awakenings is a perennial favorite, a cohort of people with severe Parkinsonism given levodopa all at once (and going through the several month long process of becoming nearly completely functional with the quirks that come from excess dopamine, then their brains slowly losing homeostasis in the face of the exogenous uncontrolled neurotransmitters).

Seeing Voices, a look into the perceptions of the deaf and the nuances of signed languages, was fascinating to me.