I was on a crowded United flight from Kansas City to Washington several years ago, and I've never forgotten it. When I went to the gate and asked to upgrade, the gate agent waved me away, saying, "I'm too busy trying to keep a family together." Apparently the travel agent had put the kids and parents all in different parts of the plane, and the gate agent was frantically trying to arrange them to be together on a full flight. I have my own family and appreciated what she was trying to do, so I simply said, "I understand," and backed away, figuring I could try to use my upgrade on some other flight. No big deal at all.
I took my seat in coach, and right before the plane was ready to take off, a voice on the public address system said, "Will Passenger Rebozo please gather your belongings and come to the front of the plane?" I figured I was in trouble, like when the principal calls your name on the PA system. I gathered my stuff and shuffled off to the front of the plane, preparing to be arrested or otherwise humiliated.
But when I got there, the attendant pointed to an empty seat and said, "We got you a seat in First." When I asked if she wanted my upgrade certificate, she said no, and walked away. I sat down, the plane took off, and there I was upgraded for free! I was surprised they even knew my name, since I never gave it to them.
I've always really appreciated this random act of kindness on the part of United. And have always felt that if the airlines spent less time rewarding the bullying loudmouths, and more time rewarding those who cooperate in helping their flights run more smoothly, flying would be a far more pleasant experience.