This is a list of every item you might take on a backpacking trip. No one would ever carry everything listed below; I select items from this master list to create smaller, specific lists of what I need for each particular trip.
PACKS
Backpack
Fanny pack
Day pack
FOOTWEAR AND WALKING AIDS
Boots
Trail shoes
Sandals
Footbeds
Wax (for cleaning and waterproofing boots)
Socks
Liner socks
Fleece socks
Insulated booties
Gaiters
Staff/trekking poles
Ice ax
Crampons
Snowshoes
Skis
Ski poles
Ski boots
Climbing skins
Ski wax
SHELTER
Tent with poles and stakes
Tarp
Bivouac bag
Groundsheet
Sleeping bag
Sleeping bag liner
Sleeping pad
Pillow
KITCHEN
Stove
Fuel
Fuel bottles
Pouring spout
Windscreen
Pan(s)
Mug
Plate/bowl
Spoon(s)
Pot grab
Baking accessory
Pot scrubber
Water containers
Thermos bottle
Insulating water bottle cover
Water purification tablets
Water filter
Matches/lighter/fire starter
Plastic bags
Bear bag and cord
Bear-resistant container
Food
CLOTHING
INNER LAYER
T-shirt
Shirt
Long underwear
Underpants
MIDLAYER
Synthetic shirt
Wool shirt
Cotton shirt
Wool sweater
Fleece top
Insulated top
Vapor-barrier suit
Windproof top
Rain jacket
Rain pants
LEGWEAR
Shorts
Trail pants
Fleece pants
HEADGEAR
Sun hat
Watch cap
Balaclava
Neck gaiter
Fleece-lined cap
Bandanna
HANDS
Liner gloves
Thick wool/fleece mittens
Shell mittens
Insulated gloves/mittens
MISCELLANEOUS: ESSENTIAL
Flashlight/headlamp and spare bulb and battery
Candles
Candle lantern
Oil lantern
Butane-propane lantern
First-aid kit
Compass
Whistle
Map
Map case
Altimeter
Map measurer
Guidebook
GPS receiver
Repair kit:
Ripstop nylon patches
Duct tape
Needles and thread
Glue
Stove maintenance kit/pricker
Rubber bands
Waterproof matches
Wash kit
Sunglasses
Goggles
Sunscreen
Lip balm
Insect repellent
Mosquito coils
Head net
Pepper spray
Flares
Strobe light
Fishing tackle
Cord
Knife
Notebook, pen, and documents
Watch
Toilet trowel
Toilet paper
Rope
Plastic bags
MISCELLANEOUS: OPTIONAL
Binoculars
Photography equipment:
Cameras
Lenses
Flash
Spare batteries
Tripod
Minitripod/clamp
Filters
Cable release
Lens tissue
Film
Padded camera cases
Books
Cards
Games
Radio
Portable CD player/Ipod/MP3 player
Thermometer