It would depend on where I was going, but I always pack a book or two to read, a camera, binoculars- just in case I get the chance to do some bird-watching. If I'm going overseas then I would take a guide to the local area and its wildlife.
I know it sounds crazy but I cannot travel without good quality toilet paper. Even in nice hotels it's not good enough for me! I also have to have a first aid kit, medications, supplements and Twinings tea-bags.