Need to get back at him!!

Ok so heres the story (bare with me) im 15, coreys 19 ( I know age thing, please dont comment on it), so he led me on all year, I knew he had a girlfriend, but he told me that they were breaking up soon and then we would date, and that once I got my car we would date, and the only thing stopping us from daing now was my parents. Well at the end of the school year, on his last day, he kissed me and his girlfriend found out, but he lied to her and told her I never exsisted. A few weeks later he told me I needed to move on, and the kiss never ment anything (he kissed me about 10 times btw). And me and my friends mindy (18) and jeremy (21) are trying to get back at him, we dont wanna have to tell his girlfriend, because he can lie his way out of it. He wouldnt care if I was with his friends or his brother. So now I really want to get back at him. Make him regret what hes done. Any ideas?! The more creative the better! Example: jeremy was gunna take him out and get him drunk, and then mindy and I were gunna silly string his car, and the 4 of us would hang out after and I would kiss him and mindy would get a picture of it and send it to his girlfriend.