I can't think of any of the top of my head. When the Fairy type was announced, I dislike them, but only because my Dragons now had hard counters.
Everyone finds different things difficult. It depends on what you're good at. Personally, I found relativity to be annoying. In trying to different reference frames for an event and how observers in each frame see the event, I often end up confusing myself and getting nowhere. Electrostatics and magnetostatics were also a pain, though I think this is more because I was under-prepared for the heavy math involved and less because the concepts were difficult.
If you consider crystals to be rocks, then yes, I do. I used to collect interesting rocks when I was young.
Nope. As a kid, I wanted to become a paleontologist to dig up dinosaurs... which is ironic considering I had (and still have) a general dislike of getting my hands dirty. As a matured, I didn't really know what I wanted to do with myself, but the decision to go into physics was made about halfway through high school.
I'm a musical and occasionally draw, so I appreciate good music and artwork (though my definition of "good music" is, admittedly, rather limited). Of the two, I think I enjoy music more.
I'm at a small (~2500 student) private college. I chose a small school because I wanted a good connection with my professors if/when I needed them (also because I didn't like the idea of taking a bus to get across campus in a timely fashion).
I use a slightly older version of Photoshop for my signatures and stuff like that. It works well enough for my purposes. My knowledge of Photoshop is admittedly limited.