what would you do with them? The first things I would do would be to wipe-out of existence all terrorists, drug lords and dealers, child molesters and rapists, and murders and traitors. After that I'd wipe-out all fatal diseases, but not the non-fatal ones (I believe people need to do some suffering) and I'm not for making the world 100% perfect. There needs to be some struggle and some work. You need to earn the right to be able to do certain things.
And for mischievous fun my absolute favorite thing to do would be to stop malevolent shape-shifting aliens (I'm hoping they exist for me to do this, using my powers to make them wouldn't be the same to me) half-way through the process of shape-shifting!!! Could you imagine what that would be like for them to be stuck between two forms (and still keeping them alive, since I believe they'd probably die if this were to happen to them)??
BUT my ABSOLUTE favorite thing (above absolute favorite mischievous thing) would be the knowledge that I'm MORE POWERFUL than ALL the superheroes and superheroines, supervillains and supervillainesses of the Marvel, DC, and other comic universes!! The Harry Potter, Lord of the Rings, Dungeons and Dragons,etc. universe (or whatever they like to call what they exist in)!! And the gods and goddesses of all ancient (and current mythologies)!! They'd all be PUNY in comparison!! In fact having Q-like power is I dare to say probably the closest to being like God (if he exists)!! Even if all combined they WOULDN'T MATCH MY POWERS!!! So what would you do?