I was there in person for Luke against Utah, for Doink, Hall to George, and 4th and 18. Tough to choose between those, but I'd probably go 4th and 18, for my live experience pick.
But my single best moment as a fan was Beck to Harline in my living room. It was just such an unbelievable moment that ended a 4 game losing skid to Utah.
My single worst was Matt Payne in Bronco Stadium. He was one of our all time great kickers, and I'll never forgive him for missing that relative chip shot. Never. Still hurts.