Huckleberry Finn. Loved loved loved that twisted little book. It's odd and funny and instantly memorable. I liked most of the stuff they had us read in school, like Of Mice and Men, I Am the Cheese, The Pearl, The Red Badge of Courage, and Julius Caesar. I always thought the problem with school units on books was feeling obligated to read them at a certain pace. My classmates hated Of Mice and Men and Courage, both of which I read in a single day. If I waited for everyone else, I probably would have gotten sick and tired of them before I was done.
We also had optional units in a point based system, so I got in some good stuff in junior high, like Animal Farm, 1984, Crime and Punishment (which was a book for the advanced kids in high school), Dracula, Frankenstein, Fahrenheit 451, some Poe stuff, Journey to the Center of the Earth...