My favorite part of flying is always the approach as you land into whatever city you are flying into. I have lived in Phoenix, AZ for a few years now and I'm lucky that every time I fly into the city I get a great view of the valley. At one point I was living in a high rise building downtown that was directly under the normal flight path, which allowed me to get a nice overhead view of my neighborhood.
One thing I still would love to do sometime is take a helicopter flight over some major U.S. cities like New York or San Francisco so I can take some photos. I know that some helicopter tours offer this where they will remove the doors and attach you to a harness that allows you to lean out of the helicopter to get the best shots possible.