1996 USC vs. UCLA football game at the Rose Bowl. UCLA came back from a 17 point deficit in the 4th quarter to win in overtime. I experienced just about every emotion wathing that game. Total frustration when 'SC started to romp us, total disbelief when we tied the game and elation when UCLA won. I'm glad I got to experince it first hand.
A close second would be when UCLA beat USC 13-9 to knock them out of the BCS title game.