Hmmm.... do I really have to pick just one power? But there are so -many-! I'd love to be able to read minds, but -oh- the ramifications of doing so... it's a real double-edged sword. I'd probably be driven insane from knowing everyone's true thoughts. I'd love to be able to morph / shapeshift. And actually take on the attributes of whatever / whoever I shifted into. Teleportation would be epic. (I envied the protagonist of Jumper SO. damn. much. Just look at or think of a place and BAMB, you're there.) And then there's the movie "Push" ... gah. I fan-gushed over that for at least a week after I saw it. Telekinesis, mind control, clairvoyance, the "mending" one...
Avatar (not the one with the blue aliens, the cartoon) was a great example of the versatility of elemental powers. Control water, and you can suck the life out of anything that needs water--which is EVERYTHING ALIVE ON EARTH, or use people and animals like blood-puppets, make snow, create rain, cause droughts, melt icebergs, part oceans, move clouds, use your own -sweat- to tear down a prison cell... and that's just ONE element.
The human imagination is just too big to pick just ONE of all the incredible abilities we could dream up.
If this -was- a world where everyone had powers, Rogue from X-men would be an epic character to emulate. Touch someone, borrow their powers, do -anything- you want. (...Except, you know, have sex... or even just hug someone without gloves and other proper protection. Needs a downside, you know.) Of course, in a world where it's just me who has powers, yeah. The ability to voluntarily bring my imagination's creations to life would be great...
However, I say "voluntarily" for a very good reason. In a world where my imagination comes to life unbridled...? You're all doomed, and so am I. I have very, very dark dreams. As for a name... Nightshade, perhaps. It was part of my previous writer's alias. (And has nothing to do with Nightcrawler. Nightshade as in deadly nightshade. Yeah, the plant. Go figure.)