My answer is of course flight, because it would be SO MUCH FUN! I would have to figure out a way to monetize swooping, because that's all I would ever do.
More broadly, one can ask: "So if you could have any superpower, what would it be?"
My brain always wants to go super-meta on questions like that and pick something like "the power to give other people any powers!", but if I can resist that temptation, I usually pick teleportation or shapeshifting. If I'm making an RPG character, those are the abilities I always gravitate towards.
Lately, however, I've found that when I'm daydreaming, I fantasize more about having some kind of ultra-charisma. All you'd do with it is turn it on and have conversations with people, but because they would really care a whole lot about what you think of them, they'd listen really hard to what you had to say. And it would be the most effective power ever.
Like, Doctor Doom shows up with an invasion force, and you run up to him and say "hey, Doom, yo, why are you blowing everything up? Don't do that, man, that makes me sad. Sit down, let's talk about this." And Doom's all, Wait, no, is he mad at me? Have I made him upset? Oh jeez, man, that's no good, maybe I better rethink this whole plan. No big fight, no collateral damage, no busting out of prison three weeks later with a new dastardly scheme, you just talk for a bit and then he apologizes and goes back home and never does it again because he feels so bad about it.
And to deal with Evil Time-Traveling Super-Hitler or whoever, you simply turn the power all the way up to 11 and tell him "Well, I must say I am a little bit... disappointed in your choices," and you give a tiny little sigh and the very smallest of sad looks and it's so utterly emotionally devastating that his head just explodes.
What superpower do you daydream about?