OK. Here it is. If it were me, I'd get the tank, BUT, your 15...Go to the GAME. Man, that ONE game will be a lasting memory for the rest of your life...especially if your a die hard fan of either team, but a casual fan of both, the memory will still be there. Take your dad, or your best friend. It's all about the memories, and later on...like xmas, talk everyone into getting you a tank.
Ps....I originally voted for tank, but after thinking about it, this is my final answer. lol. You'll have fun no matter what though.