I want to be able to control people's bodily functions (think Heartrender's from Six of Crows, if anyone knows what that is).
If not, I'd just be a fire bender. That's a super power technically haha.
Flight flight flight! Time travel/manipulation second probably
I'd like invisibility, but somehow the idea of it scares me... having someone invisible in your room for instance
I think freezing time would very practical for me, as long as I don't age (or anyone else) while everyone else is stuck in time. I could use it for tests and working on projects and doing a million things in a day without stressing about having to get everything done. Plus I could pull pranks on people that get on my nerves. I'd probably spend more time freezing time than not freezing it if I could do that.
But being able to time travel and become a former version of myself would be pretty cool, too (i.e. instead of the kind of time travel where there's two of you, there'd only be one, and you'd inhabit the body of your former self during that time). I could redo all the mistakes I've made and start over my life from scratch!
Mind control, telekinesis, invisibility, and shapeshifting would also be very useful as well.