A Removable Storage system provides two classes of media pools: system and application. System media pools include free media pools, unrecognized media pools, and import media pools. Removable Storage creates one free, one unrecognized, and one import media pool for each media type in your Removable Storage system.
For obvious reasons a camera is really nice to bring along. Big plus if it's a digital camera! Other items: a whistle, in case you get lost or need help ; waterproof matches ; some kind of lip balm/blistex ; sunglasses ; extra batteries for that flashlight! gaiters are great if you're hiking in shorts and it's a bushy or wet trail
Water:By studying the weather, the water sources, the trail, one can carry the minimum amount of water, which is probably the heaviest thing one carries on a day hike. An interesting idea is to stash water bottles on the way up, to be retrieved on the way down.