I'd like to go back to Roman times or Victorian times - however in both cases, I'd like to be in a position of privilege (well, not so actually, I mean these times were not nice if you were at the bottom of the foodchain).
Oh yeah, I'd like to be 12-21 again, and shag more, turn up to lectures more, and get a decent job from the outset, instead of being crazy and running up debts.