Unique? Try Аниме cosplay! For instance, I'm going as Crona from Soul Eater, that's pretty unique. The best part about Crona is that s/he's genderless and doesn't have many traits that distinguish it's gender, so Ты can go as it no matter what gender Ты are. An awesome touch is getting the sword или the Ragnarok stuffed animal to put on your head to mimic how it get's tortured by Ragnarok all the time.
honestly, Ты dont have to be from a movie. ask them to think of somthing horrifying, and dress like it. i make my own costumes, so its acually quite easy if Ты know what to do/use. if Ты choose this and need help, just write on my wall.