Well for me i would say my first yankee game with my father but i cant remember anything about that game just that they lost. So ill have to go with going to game 2 vs the twins in the 2004 playoffs with my father as number 1. The yankees won in extra innings(also got my first BP ball).
But close behind is a game that Jeter hit a walk-off homerun vs the red soxs in the bottom of the 9th in 2005. I had brought 2 of my friends and we all got BP balls which was cool.

And for fun, some of the bad games i went to is that i witnessed Mariano Rivera blow 5 saves. I guess im bad luck.