For me it would be:
The ability, by thought alone, to cause any living being to explosively evacuate their bowels. This power to have unlimited range and no limit on the number affected. I could use it on an individual, small group, an entire town, a whole country, a continent, the world.
I scare myself when I think of all the possibilities, but the Merry Prankster in me loves it.
The same as the first wish I’d ask for if a genie offered me 3: Knowing the consequences of my actions before I do them (including speaking or asking for a particular wish).
I’d like to have the ability to turn back time. I would use it to prevent Cher from recording Turn Back Time.
The ability to heal by touch.
You’re putting Cher in a causality loop? Good!
Super speed for me; clean the house in 2 minutes.
Teleportation. Man, I hate traffic. And parking.
Invisability. I’d love to sneak around at will.
^ Will who?
The same guy who gets fired at all the time, of course. 
(For me, the answer is flight.)
The ability to force people to answer me truthfully, no matter how I ask-in person, over the phone, and even by printed word.
A modified form of time travel; only forward, but faster or slower than “ordinary time”. Spead up or slow down by up to ~10,000 times. At fully sped up it’s kind of like “super speed”; at slowed down, I cold make a lot of boring waiting for X to happen pass in a reasonable (subjective) time.
Teleportation for me! I love to travel, but getting there takes time, and airline tickets are expensive.
Goddamnit. This was mine. I have coworkers that can attest that I’ve been wishing for this power since maybe '08.
I guess I should pick something like super strength so I could go fight evil. But, man, teleportation sounds really good. Much of the stress in my marriage and my life generally has come down to not living where I wanted to live. If I could simply teleport anywhere at will, and ideally take a few people with me, I would have avoided so much conflict.
Also, I shudder to think how much time in my life I’ve spent driving. If I could have just zapped myself from place to place, I could have spent that much more time sleeping or spending time with my family.
As specific kind of immortality, more like reincarnation. At the moment of my death my consciousness, soul, what-have-you would be transferred into that of a new-born child. And I mean *really *new born, as in my last breath to his first breath (it would be a him because I don’t know how to be a woman or anything else). The memories of past live(s) would only become available to the new “me” with the onset of adolescence, slowly at first, growing until “I” had all “my” memories by the age of 15-17. I’d have no control over where I reincarnated, nor over the socioeconomic position of “my” parents. If the wish-granter is powerful enough I’d like to have born for the first time in the Chalcolithic era, so I can/could have observe all of human history.
If you think about it it’s the perfect form of immortality. I’d have diverse upbringings to give me perspective and compassion. I’d have the wisdom of millennia help me make the most of what I have. If things go too far sideways I can always kill myself, secure in the knowledge that I’m merely transferring my “self” into a new vessel. It also sidesteps the usual problems that come with immortality. No one would notice it, so I wouldn’t have to set up some elaborate scheme to keep people from catching on. I wouldn’t have to worry about being trapped in a chest at the bottom of the sea or anything like that. And when humanity goes extinct I’d go with it. And even if I told anyone about, what are the odds they’d believe me?
Hey, have I told you about the time I spent in Ur?
The ability to make any change in my body. Eg, lose 20 pounds; lose 40 years; grow wings; cure any disease, become invisible, etc.
Immortal. I want more than anything to see how advanced we humans become.
Also, I have a theory, after you get to be about three or four hundred years old. People will start to seem like children to you and be easy to manipulate.
Beware the butterfly effect! I think you’d be afflicted with terminal indecision.
For my own part, I would like a limited omniscience: to know everything that is known.
I don’t care as much about my super power as I do about my costume. Something with a cape. And maybe a cowl, though I’m not 100% sure what a cowl is, exactly. Oh, and a codpiece.
Everytime I rolled a pair of 6-sided dice, the total shown would be 7. That’s the superpower to have.