There's a giant monster eating the front half of the ocean liner you happen to be standing on. It has intestinal parasites the size of city buses and it's specifically upset with you. Most people would scream for evac at the top of their lungs. Chris and Jill, however? Attack the damn thing. With small arms.
Jill, in a reasonably calm tone of voice: We can do this, Chris.
The second part of that boss fight is itself a crowning moment of awesome, which ends with you shooting the monster in the throat with a rocket launcher.
Let's give the final boss some recognition, while "only" tyrant-sized. He can teleport and create fake clones. Plus his theme reeks of awesome.