What should i be for halloween? (age 14)?

alright. i'm 14...and im going to a halloween party...TONIGHTT...and i have absolutely no idea what to be. i have a lot of clothes...like tutus and all that fun stuff...but i just cant think of anything! i dont want anything too inappropriate...but i also don't want to look like a 4 year old. also, i dont want anything that i have to explain to people...like a "cereal" killer...haha. i know thats a lot of things to be asking, but please give me some ideas...thanks!!