What mandatory items do YOU carry in your pack?

What pack and contents depend on factors such as what kind of trip, location and terrain, which depends on weather.

The one constant that never changes, a flask, at least.

I second Snosluts proposals-other than I don't drink, so I carry a small first aid kit instead of a flask.
1) Must Have-First Aid-Never know when you need band-aids all types, tape, blister kit, I-B hope'n(the headache goes away), emergency shelter (can be used as a reflector as well as a shelter), lotions etc..
2) Must Have-10 Essentials waterproof Fire starting capabilities, hand warmers, Food, extra clothing, sunglasses, sunscreen, compass, altimeter and map (carry your own-never know when you get separated or if your partners get lost and they have all the tools) Headlamp w/ batteries as Becky suggested. A cell phone is good if you own one and there is coverage.
3) Must Have-Repair stuff for ski bindings, skin loops, extra straps, tools to do the repairs.

I was reprimanded this weekend for not having a combat-ready daypack with skins in it.

After a Summer hike to the PG and ski all the way to base of the Cowlitz Glacier I opened my pack only to see that the skins were not there! : Luckily the snow had enough stick to it to not need them.

I own several packs based on what the tour goal is and the weather conditions.
But they all usually get MUST HAVE First Aid, Repair stuff, Food/water, extra clothing. ANY avy danger-shovel, probe, beacon.

Comfort would be the first goal of the pack, so if you go to buy a pack at a store.
Fill the pack with all the essentials that you find in the store or they have weights to put in the pack.
I like filling the pack with essentials, so it gives a realistic idea of what you need to bring and the space available.
Water can take a great deal of space and weight, so account for that or if you are going to purify water on the trip.

1200 cu in pack-Used for lift access BC or fair weather close proximity to car or home BC.
Avy gear, skins, food, water, 1st aid, tools/repair, essentials, 3 gloves (2 spring-1 winter), goggles, sunglasses, 8oz goretex pants (waterproof protection), core heat protection, extra hat.

Bit cramped in this pack size I recommend an 1800 cu in pack for day stuff then maybe you have room for a camera.

2200 cu in pack-Used for more adventurous day climbs, if the weather is gnarlier and I need more clothing or even overnight (but it fills the pack to the gills)
Fill with all the gear above and maybe a GPS, extra food and full gore-tex outfit (16oz), insulated clothing in case I have to spend the night. Layers based on conditions. Maybe even bring my Jetboil for water and meals.

The hydration systems are personal preference-
A lot of the hoses freeze if they are exposed to air.
My Osprey (2200 pack) hydration zips all the way in the shoulder strap and does not freeze. Also blow all the water out of the tube so it does not freeze.
Some prefer nagalene bottles because the flavor that often represents typical hydration systems.
I use both, but the Platupus plastic water sleeves are handy because they conform to the pack when filled instead of being a bulky plastic bottle. They come a variety of sizes and don't have the aftertaste of plastic.

Good luck
Joe

When I venture out to the backcountry, I carry my personal first aid kit, fire starter, extra food, avy gear, etc.  Depending on snow conditions, I usually take my ice axe as well - it works for a variety of conditions (ice, wind pack, etc.).  I also carry an extra binding strap (snowboarding) and a Gerber multi-plier for emergency repairs.

One other thing that should go w/o saying - a good map of the area and a compass with the know how to use them.  Sometimes I'll take my GPS if I'm above timberline or I want to fool around with it.  I use a Dakine Poacher backpack (2300 inches) because it can carry my splitboard well if I need to put it on my back.

Go Joedabaker Go!!!

I want to go with Joedabaker, he carries all the stuff that I've since pared down doing 900' corndogg'n. Sounds like between he and Snoslut we all could get loud and rowdy late into the evening.

PS, if you are going to take binding parts...remember to bring all the correct wrenches and screw drivers.

My pack is different every time I am out but I almost always I carry the following:

For first aid:
1. three essential drugs: ibuprofen, benadryl, and NoDoze -
2. duct tape(roled on my poles) its good for blisters too
3. down jacket

Fire starter - in an emergency - you can cut a strip off your climbing skins

Petzel Zipka Headlamp (specs: 4LEDs, three settings and a strobe, retractable cord - very sexy)

fleece skull cap, knit nylon gloves and capilene balaclava

avi gear

Snickers - it has more fat than almond joy and hence more calories for its weight! A Stanford study found it a better meal replacement for athletes than Power Bars.

I have a little mammut pack with side straps for skis and a back pocket for my shovel and down coat. I am shopping for something a little bigger that will fit my ski boots for summer time.

Snickers - it has more fat than almond joy and hence more calories for its weight! A Stanford study found it a better meal replacement for athletes than Power Bars.

Among some of my friends, Snickers are known as "Ballard Power Bars." This is not for nutritional reasons (the Stanford study is news to me!) but because we are the sort of skiers who drive to the mountains with our seatbelts dragging on the pavement and our turn-signals on.   

Now this is a topic I can sink my teeth into! What is your favorite cheap energy food? Gu and Cytomax (whatever they are) don't count. It has to be the sort of thing you can buy at Safeway in Ballard.

Snickers? Payday bars? Swedish fish? I'm still on the lookout for the perfect energy food for cheapskates.

Climber's lunch: 1/2in slice slab cheese (5 lb blocks you buy in dairy section), two thick slices salami, two pieces wheat bread.

Nitrites in the meat make it slower to spoil (Ive had one last three days). No less appetizing when crushed (unlike PBJ). Make up ten at a time in five minutes, stick em in the freezer, and on way out door grab a couple. Good in summer too since they soften up in the heat (only good for two days then).