Cool things to put into a treehouse?

See if you can have one of those neat fold up chairs that becomes a bed - one that you could cover with a plastic sheet when not up there. How about a small set of shelves for games / treasures. Get some plastic storage boxes to keep your things in so they don't end up weathered. Be sure to have a good light source - a flashlight and one of those florescent lamps that run on a 9volt battery. An indoor / outdoor carpet would be great for the floor. A metal box for snacks -- a change of clothes, a blanket that you can store in a plastic tote with cover would be really nice.