Like a usable item? *purchases 99 Rinoas*

Since you took Rinoa, I'll have to say Selphie. She sacrifices herself to save the party from a deathtrap, but nobody even really mentions it. One character will just say "Selphie...", and then the party will move on through whatever area it is. Just to accentuate her uselessness, she's the main character. And whenever she says something, the party ignores her.