Most disappointing at the time was 1965 SC-UCLA. I was a freshman and looking forward to going to my first Rose Bowl. With 4 minutes to go I had already lit up my victory Tiparillo (so cool). I dressed in black for the next week.
The most disappointing in retrospect was the Rose Bowl game against Texas. So much at stake and so many things went wrong. By then I was mature enough to wear normal clothes after the game, but what a missed opportunity to achieve a three-peat.