It would be the ability to sit very, very still.
This is a superpower in my current possession, but I feel I’m not making the most of it.
With the exception of my hands and fingers, I am so focused and unmoving when I write that I no longer feel heat and cold in the external environment. It’s only after the writing that I notice the blue tint to my extremities.
As to what I could do with that superpower? Well.
I could make money by allowing venomous snakes to slither over me. I like snakes; they wouldn’t bite; they would think I was a dead tree. People would pay for the spectacle.
I could use my very cold hands to chill approaching fires. Instead of dumping water over a bushfire, the fire department could dangle me from a helicopter at a proximity to the fire that would kill most people–but not me. I’d quell it, because I’m super.
I could repel bad guys by threatening them with my frozen fingers. What man actually likes the feel of his partner’s cold hands or feet against his skin, stealing his warmth from under cover of doona? It would be sufficient to spook that burglar out of my house. [Note to self: come up with alternative plan for female intruders.]
I could stop wars. I would be under the radar in the case of a military invasion: my coldness would prevent me from showing up on infrared viewers. Then, when heavily armed strangers encroach on my domain–Wham! I would leap into action, with my pens and computer cables and such braveness as I never knew. It would be pitch black, on account of the baddies cutting the power before moving in, so I would have the home layout advantage.
Or I could just write. Maybe engaging others to feel or see life in a different way is a superpower in itself. Maybe this is how I’ll save the world.