1. A cell keychain. This can be plant or animal, depending on your preference. This is, of course, necessary for impromptu exam revision as well as stealthy admiration of the Golgi Apparatus.
2. A subscription to New Scientist. Perfect for weekly updates on the scientific happenings in the world, plus it gives you something legitimate to read in compulsory Physics classes.
3. A University level textbook.
Y'know. For light reading. (My dad thought it looked good, so he decided that it should become part of my extra work requirements. And you know what? If you're into this kind of thing, it's seriously interesting.)
4. A severe hatred of physics.
No biologist I have ever met actually likes physics. Chemistry, however, is neutral ground.
5. A genetic condition with a cool name.
Mine's central heterochromia. What's yours?
(Sadly, this is not my eye.)