What Move Did I Play Here?

Guess the move that lead to a nice upset win over a highly opponent. First person to guess will get to play me a 15 5 game here on chess.com along with analysis after the game for free! If you would like me to do further analysis (opening, computer analysis, etc.) of your game please give me your email address I will send it to you ASAP. Leave your answers in the comments below. Good luck!