Many people spend a lot on gear that isn't entirely necessary, so consider carefully what you need and remember that if conditions are horrible, it is unlikely that we will be climbing. Conditions may worsen during the day but if that is the case, we will be on our way down.
However, if you are a real climber and don't mind climbing in rougher conditions, should that be the case, then bring good gear and we won't waste an opportunity.

What to expect

When it is sunny with no wind a thermal top is enough, backed up by a fleece or light down jacket for rest stops and a windproof breathable jacket for when the wind picks up (Gore-Tex, Windstopper or similar).

Gear list

This assumes you have all the trekking gear like warm hat etc. The majority of this gear is available from us or in Kathmandu , and some of it can be rented.
+ high quality sunglasses. Side pieces are not essential; we can always use tape for a day. Ski goggles are unnecessary.
+ neck gaiter or balaclava
+ balaclava, only if you don't have a neck gaiter
+ new liner gloves (ie thin gloves)
+ fleece gloves/windstopper gloves
+ windproof gloves/mittens if you don't have windstopper ones.
+ trekking pole
+ ice axe, non-technical is generally better
+ crampons
+ light harness (Black Diamond Alpine Bod is perfect)
+ jumar
+ belay device: ATC or figure of 8 etc
+ two locking carabineers, two ordinary ones
+ two prussics, one short, one longer
+ windproof pants - these don't have to be fancy and you can buy in Kathmandu cheaply
+ snow gaiters
+ Plastic boots/leather boots - see the discussion below
+ leather boot waterproofing (snow seal etc)

Sleeping bag

Down-filled bags (4-5 season) are the best to bring because high altitude nights will be cool, and there is nothing worse than to be cold at night.
Sleeping bag liner
Cotton, silk or fleece. Saves washing your sleeping bag and adds warmth. Cotton or silk ones can be made in Kathmandu but are more easily bought from home. Fleece ones is readily available in Kathmandu and will cost you next to nothing.
Daypack
This should be comfortable and a good waistband that transfers some of the weight to the hips is most important. It needs to be big enough to take a jacket, fleece, water, camera and odds and ends. You pack your daypack in the morning and give the rest of your baggage to the porters. You should have everything you need trough the day with you, since it is likely that we don’t see the porters again before we camp for the night.

Down jacket

This is something you don’t want to miss on those cool evenings. If you don't already have a down jacket they can easily be rented in Kathmandu for around $1 a day.

Helmet

It is always sensible to climb with a helmet, but it is one more thing to carry and only use for a few hours. For the trekking peaks it is rare for climbers to use a helmet, but that is your decision. On Island Peak rockfall is possible but rare.