I've always been a sucker for teleportation. Mainly because when I was growing up, I lived really far out of town, and travelling to school and to see my friends took ages!
There were so many nights when I wished I could just teleport straight back to my cosy bed and fall asleep, instead of having to take night busses across town in the cold.
Nowadays, it would be doubly cool because it would allow me to travel a lot more, and in a far more cost-effective way.
Seoul, Korea? Ping! I'd be there in seconds... Without the overnight flight.
Snorkeling in the Cayman Islands during my lunch break? Don't mind if I do!
In terms of being a superhero, and using my super powers for good... I guess I could rush to the scene of accidents and then transport people to hospital pretty quickly.
I'd also make a great undercover agent. Popping up out of nowhere, foiling a criminal plot, and then vanishing into thin air again before anyone knows what happened.