Which of the following famous movie lines was improvised?

Some of film history’s greatest lines were completely improvised. For Robert De Niro, his mark on “Taxi Driver” (1976) was this much-quoted line. According to the film's director, Martin Scorsese, the scene in question was shot during the last week of filming and had no dialogue written, so Scorsese asked De Niro to say something to himself in the mirror.

The director said De Niro kept repeating the line, “You talkin’ to me?” While the assistant director was trying to move the scene along, Scorsese knew what he had. He said, "It was like a jazz riff. Just like a solo.” Humble as always, De Niro downplayed the iconic line, saying, "You never know with any of that stuff. You just did it."