A spy! Having all the cool gadgets, flouncing around suspicious facilities, throwing sharp things at people I don't want living anymore, uncovering conspiracies... it'd be amazimg
But a slightly more realistic (and less dangerous) one would be a journalist! Because then I'd still get to snoop around shady places with a huge camera and uncover devious plots! Maybe, or I'd just report on some kid with cancer or the opening of a new park xD Too bad journalism doesn't pay very well... *sigh*