All hail Frank Bryce, the only Muggle to mock Voldemort towards his face. True, he did die, but the old man had balls of steel, befitting of a World War II veteran.
"Lord, is it? Well, I don't think much of your manners, my Lord. Face me like a man, why don't you?!"
Cedric, Fleur, Krum, and Harry in the first task of the Triwizard Tournament.
In the second task, Harry stubbornly refuses to leave other prisoners; he comes in last but is awarded second place for his "moral fiber", as Fred and George put it, and more importantly wins respect from the other competitors.
Harry and Cedric deciding that it didn't really matter which one of them won the tournament, instead just doing it for the honor of Hogwarts. In hindsight, this may not have been such a good idea.
Don't forget the first task, where Harry uses his Quidditch skills to face against the dragon and get her egg. Even the judges weren't expecting that!
Bagman's reaction; particularly this bit once you realize who's being told to see Harry in action:
"VIKTOR KRUM ARE YOU WATCHIG THIS?!"
When Harry stepped forward to face Voldemort. He knew that he was about to die. But he would not die crawling and begging for mercy. Daniel Radcliffe's expression for that moment just sold it. Completely.
Harry vs. the Horntail. The book has the Horntail just guard the golden egg, and stay in the arena. In the film, the dragon breaks free from it's bonds, and chases Harry throughout Hogwarts. The special effects are absolutely amazing.
The Dark Mark. In the book, it's described as basically a green constellation shaped like a skull vomiting a snake, but in the movie, it's much cooler and dynamic-looking. Not to mention, Death Eaters apparate out of it.