There are a few basics that I never go caching without:
The GPSr - my wonderful Garmin GPSmap 60 Csx...well I wouldn't be caching if it didn't come with me
A pen...not just a normal pen...I prefer a nice gel pen as it will write on everything
My caching note pad - to write all of the GC numbers of the caches I have visited with a brief description so I can remember them when I log them on the computer
Travel bugs and Geocoins - The trackable items that travel from cache to cache
My iPhone - not just for safety. It has the geocaching application loaded onto it, so if I'm ever stuck, I have all the information at my fingertips
Spare batteries - well I wouldn't get very far if my GPS died would I?
Caching labels - To stick in the log book's..it has my logo on with space to write a comment and the date
Money - You never know when you will pass a nice pub or a chippy
Maps - yes I might have a GPS but having a map is essential to know exactly where you are
Camera - So many beautiful places to photograph
Car keys - I wonder why???And the not so basic stuff:
- First Aid Kit
 - Head torch - for the good old night caching
 - Waterproof jacket and over trousers - Love my Berghaus paclite's - lightweight and waterproof
 - Bag of swaps - little things like badges etc
 - Food - especially for long walks
 - Mars Bars - an essential snack
 - Water - carried in my camelback water re-hydration pack
 - A leatherman tool and a gerber tool
 - Toilet paper - well you never know when you need to blow your nose!
 - Suntan lotion - (in England I hear you ask?)
 - Lipsalve
 - Antiseptic handwash - after all you end up scrabbling in all sorts to look for caches
 
For those long hikes:
- A silver heat blanket
 - A rescue beacon - A little device that flashes infrared light in case of emergencies.
 - More food
 
And in the car
- Dog food and loads of water
 - Towels
 - Spare clothes and shoes
 
I'm sure many other cachers would travel more lightly than this..or would carry different things. These are the things that I can't live without and make my caching trips easier.
I wonder what you would carry in your rucksack??????
