Learn to handroll cigarettes. Save money, look much more badass.
Read - especially if you don't have a solid background in math and sciences. Chances are, you don't like or hate math or know if you're good at it or not because the vast majority of people everywhere have never seen real math... give it a try, you might wind up seeing the world in a more logical and understandable way.
Let your mind wander and take notes - never know what bizarre tangents you can get back to later.
Let your mouse wander on Wikipedia.
See what slightly deviant things you can get away with before the boss finds out... ThinkGeek has toys, the internet has annoying noise generators, a children's toy store has Legos aplenty, just start acting on whims and seeing what comes of it.
Jeff