Mixed Party Ideas - 15 Years Old

Hi!
Well i have a slight problem, im turning 15 this year and i was hoping to have a mixed party, with girls and guys from my year.
My birthday is in december though, which i don`t think is really convenient seeing as i love the summer =P
But i havent had a party in a while and i figured, what the heck, so i was wondering if anyone had ideas for a mixed party?

One of my friends suggested a Dance, but i want to get more ideas...

Thank you so much!
M.