What one thing (or more) from your chosen fantasy-universe would you want to be a thing in our universe?
The immediate thing that came to mind when reading this question was the magical cell phones from Pretty Guardian Sailor Moon that can change your appearance. Essentially when you take a picture of an outfit and press a button, that outfit appears on your person fitting perfectly to your figure regardless on how it originally was laid out. I've always thought it would be very useful and convenient, and would waste less time trying on clothes that don't fit.
Of course there are an endless list of things I would choose that could become a reality in our world. Like some of the magic from Harry Potter, particularly in terms of various transportation methods, or perhaps an actual Stargate where you can travel to different places around the world in an instant, or the portal gun and long fall boots from Portal because how cool would that be, or the holoband from Caprica where you can go into an actual virtual world, like meeting your actual online friends in a 3D virtual space and doing whatever you wanted to do, within reason of course. There are just so many possibilities...
There are still a few more days left, for anyone who wants to ask a question for me to answer.