Director - Christopher Nolan

As the Joker (Heath Ledger) waits quietly alone in jail after having been arrested by Jim Gordon (Gary Oldman), Mayor Garcia (Nestor Carbonell) shows up to look over Gotham's latest scourge. While there he also promotes Gordon to the position of Commissioner.
As the officers in the room applaud the announcement Ledger begins, unscripted, to slowly clap - never changing his facial expression. It was just a simple improvisation but one that was unsettling and darkly brilliant.