What Should I Write?

I'm in my third year of medical school and soon I'm going to write a "skripsi". How do you call it in English? Thesis? Dissertation? Paper?
I haven't decided what I should write yet. 
I spent two years of medical school in "darkness" so I don't know which field is interesting or easy to write. Some fields are interesting to learn but painful to write. Others are not interesting to learn but easy to write.
I guess I should read first.