We actually have a little more than 6 hours at our disposal during our Hong Kong stopover, but I’m being conservative here.
1. Take your own (self-guided) tour encompassing the Peak Tram, the Peak, the Star Ferry, and Tsim Sha Tsui promenade. This website has a suggested itinerary and gives you the approximate timing for each stage.
2. Visit the giant pandas (LeLe and YingYing), and ride the cable car, at Ocean Park.(Citybus #629 from Central Station).
3. Check out The Peninsula Hotel.
6. Shop till you drop, at the airport or at these places. Or you could make the trip out to Stanley Market by taking bus 6, 6A or 260 from Exchange Square. It's a 55 minute ride, so you have to be keen!