I would be a waterbender! It's my favorite bending style from the series simply due to its versatility and OPness! You can freeze people and objects: Heal the Sick: Annndddd...Need I even mention Bloodbending?
Id choose invisible time travel. Im obsessed w how ppl lived decades and centuries ago. Id love to see it, but I choose the invisibility cus I aint trying to be put to work in 1820 Alabama.