Any scene with the dragons. Especially when it's the alpha male.
Watching the male slowly burn down Van Zan's entire army was full of awesome. Even if it was supposed to be kind of sad.
The big male surely rated as the most Badass dragon ever featured on film to date.
Van Zan is so full of himself, that it's awesome.
The part when the Americans arrive.
Quinn outracing a dragon on a horse, so that Van Zan can kill it.
It may be that Reality Ensues straight after, but seeing Quinn punch Van Zan in the face for trying to conscript his people was awesome. And even after it became apparent that he was losing, he kept getting back up.
He had seen the first dragon wake, survived without his mother from an early age while the world was going to crap around him, he learned to forage, grow food, build things and is such a natural leader that even when he doesn't want leadership he is the defacto leader, he organized dozens of survivors, manym more skilled then him and harnessed those skilled people to build things in cave with a box of scraps to ensure the survival of all. That is not the kind of man who stays down in front of anybody or anything.
Three humans against one very large dragon. Enough said.