Well, there are quite a few things that I have become passionate about, and I have already photographed a few of them.
I will have to dig deeper into my list of interests, and hopefully come up with something.

As far as shooting something that I am uncomfortable with; the truth is, that I have become quite comfortable behind the lens over the years.
There are really only two areas that I can currently think of, that make me uncomfortable; photographs where I would be financially liable for messing up and nudes.

This discomfort would be at the financial and interpersonal levels though, not the technical level.
I have this image of either being sued for messing up an important event in someones life, or getting smacked repeatedly for asking people to model in the nude.