Gosh I thought I carried a lot until I saw some of these lists!
I carry the following stuff, in a smallish shoulder bag-
GPS (obviously)
Spare batteries
PDA with mapping and bluetooth GPS unit
Notebook
Pens
Multitool
Tweezers
Spare container
Adhesive tape
Magnets
Zip ties
Garden wire
Bite/sting spray
Mobile phone
Umbrella
Waterproofs
Bottle of water
Grain bars
Mind you, having read some of what everyone else is carrying, I think there are one or two essential items that I might need to add to this!