10 Best Unscripted Movie Endings Ever
5. I Am Iron Man - Iron Man (2008)
Before the MCU was the cultural juggernaut it would soon become, there was just Iron Man, as played by the perfectly cast Robert Downey Jr from his 2008 debut to his heartbreaking sacrifice in 2019.
Throughout the franchise, Downey Jr was known for his rapid-fire ad-libs, but no improvisation was more effective than his final line in 2008's Iron Man, where he gives a press conference about everything that's happened in the movie only to scrap his original plans and proudly proclaim: "I am Iron Man."
According to super-producer Kevin Feige, the actor fought for Stark to reveal to the world that he was Iron Man, which he agreed with on the basis that in was totally in character for Stark to take the spotlight, and because it was in-keeping with the tone of the comics.
As also noted by Feige, Iron Man's final scene changed the MCU forever, and in a beautiful case of things coming full circle, Downey Jr actually improvised the same line in Avengers: Endgame, where Stark's death was originally written without the superhero saying a word.
Further proof that Downey Jr was the best man for the job, if you ask me.