James and Lily To establish the story line as well as to show orphans of war.

Cedric Diggory To show Voldemort's mercilessness.

Sirius Black To show Harry's lack of guidance/parental figures.

Albus Dumbledore To show the death of a great leader can't stop a war.

Hedwig To show the end of Harry's childhood.

Mad Eye To show the death of a solider.

Dobby To show even the smallest of creatures can die a Hero's death.

Fred Weasley To show that some deaths you just can't get over. And that's okay.

Tonks and Remus Lupin To reestablish orphans of war.

Colin Creevey To show that the good die young, even when they aren't supposed to.

Severus Snape To show that you can always change your ways. Always.