This is easy.

As a child, I always wanted to be able to shoot spiderweb out of my wrists and fly through the air, latching onto sides of buildings. Since I have twice been bit by spiders, I don't think the chance of me developing this ability in any kind of natural way is going to happen.

So, I would create some sort of gadget that would allow me to do just that. Shoot web. Attach to buildings. Fly through the air.

That would be awesome.