...it would be the ability to eat as much Nutella as I want without absorbing any calories.
I try not to worry so much about such things too much but Nutella is so, so bad for you (seriously it's all sugar and fat with very little actual hazelnut). But so, so good for the soul.
I'd also like teleportation ability. Honestly that one would probably be more useful but seriously. Nutella. Om nom nom.
What superpower would you choose?