Party for 15 year old themes?!!?

I need a party theme. It's in October. I'm turning 15. Inviting about 15 girls. I need something REALLY fun, just for the day. something interesting. last year i did a chocolate theme w/ candy bingo, chocolate dipping and creating stations, chocolate tasting, find the choc. in the choc. whip, pin the flag on the hershey kiss.... you get the deal. IT NEEDS TO BE CHEAP. best answer will be theme idea that's fitting to my needs, cheap, and FUN! THANKS!