Out of all his movies, and I've only seen about half of them, the one which stands out in my mind head and shoulders above the rest is
One Hour Photo.
What impressed me most is how out of character for him his character was. Totally against type. And he nailed it.
But so many stellar performances!
Moscow on the Hudson
Good Morning, Vietnam
Dead Poets' Society
The Fisher King
Jakob the Liar
and the list goes on.
One thing which surprised me in the barrage of tributes is he was from Chicago. His home and much of his early work was here in the SF Bay Area, I thought he was from here.
He was 5 months younger than me. :-(