(a) to levitate/ fly so that I could get to places quickly without long boring journeys
(b) to be invisible / intangible. There are a few people I'd like to haunt, so I would want to have fun being a poltergeist.
(re) re bluedolphin's idea : I would like to be able to time-travel, but only as an observer, not as a participant. i.e. be able to be there, but not be seen by the local people. I believe that LHO acted alone in killing JFK, so I would like to be able to go to Dealey Plaza on 22.11.63 and actually watch him do it - just for the satisfaction of knowing the answer for certain one way or another.