I'd probably go around and find my enemies and make their day crap, like tripping them and slapping them just because. Then I'd reward myself by going into the kitchen of a nice restaurant and eating whatever I fancy.
Make my way up to AQA headquarters and peer over all the examiners shoulders and get my results. Maybe add a couple of stars to some (although a B* doesn't make sense now does it?)
Never-ending heists.. except it would get boring quickly, so I'd end up challenging myself by putting all the stolen materials back for kicks and giggles
Just curious... why does it have to be an expensive gym?
@moggis you could try a few gyms ranging in price and quality and see which offers the highest standard of eye candy. You could theorise that the more expensive, premium gyms would have a higher percentage of older ladies or men, where as the slightly cheaper gym may attract the younger demographic.
If you ever do become invisible for a day let us know how this question concludes.
Troll everyone at work by moving their stuff around randomly and setting trip wire traps then being unable to contain my laughter at their looks of confusion.