For me personally, Yinsen's death and his final words to Tony. If it wasn't for him, the MCU would have been a very different place.

Iron Man firing a tank missile and walking away from it as it explodes

I gotta go with the very first time he suits up. Such a badass moment and the beginning of an era. I’d also say the very last scene of this movie ranks among the best final scenes in the MCU

The part where pepper gives him a gift. "The proof tony has a heart box"

When he eats a cheeseburger. I just really relate to that personally

Lol

The I Am Iron Man scene.

Yinsen's final words and "I am Iron Man" :')