Flight. And not just superman's powers, any power ever!
Yes, it's heroic possibilities are limited. I mean, you could only carry as much as you could on land I suppose.
But you could save a baby from the top floor of a buiding that's on fire (you wouldn't have to worry about falling through burned out floorboards either).
You could fly a hose right up inside it quicker than the fire squad could sort it out.
You could rescue children or small animals that have been caught in a current at sea or in a river, and fly rescue rings to those you can't carry.
You maybe couldn't catch people whose parachutes didn't open, but you could pull with all your might and slow them down as much as possible.
In floods and earthquakes or other natural disasters, you could bring supplies to people trapped on their roofs where no one can quite reach them and take whoever or whatever you can carry to safety.
If there was a criminal on the run, you could act as a police helicopter would - fly up high enough that you can see which field they are running through and where they stop to hide when they think no one is looking.
That's just what I can think of off the top of my head.