In a non-ironic way characters
The characters are the ones that should move the story, they are the people you will end up remembering and they are the characters you will want to spend more time with.
On the other hand my entry to the contest would be a subversion of expectations.
Nothing better than killing off the character that all your readers love just for the sake of surprising them without any idea of how that might realistically impact the story. The protagonist has just lost his girlfriend, the girl he knew since childhood and who could finish each other's sentences. Yes, his death will surprise the readers because she was hit by a 100-ton anvil that materialized just at that moment, then make the protagonist forget about the girl's existence in the next chapter.