I enjoy shopping for everything, even the stuff that is hard to fit or very boring/practical.
The top of my "fun" list is probably gear and knitwear. Gear is fun because the technology behind it is always changing. Knitwear (especially at secondhand shops) is fun for the opposite reason -- it preserves traditions! Even though I haven't bought much knitwear the past few years, I could spend all day looking at old fair isle and fisherman's sweaters. (I know SarahD8 gets it!)
Shoes and jeans are the most difficult due to fit and comfort issues. It takes me a loooong time to find what I need, but when I do, it's very satisfying!