Please tell us what is your budget for lightening your load, as well as what are some things that are a "must have" versus negotiable.
To have a serious evaluation, you need to weigh all your gear. first aid kit, food, clothes, electronics etc. so you can make an educated decision if item X that you rarely use is worth the 15 oz of trail weight. at least do an Internet search for brand products to find the listed weight on the specs page. Go to REI sporting goods, they dont mind if you weigh your gear using their store geal scale. Just let them know in advance so they dont think you are stealing.
Is your backpack bag comfortable with 20 lbs but hurts at 40 lbs? I ask because if the bag will hurt at any weight, then we can address that issue separately from weight reduction.
You stated that you are backpacking for 10 days straight. at about 1.5 lbs - 2 lbs of food per day, that's 15 to 20 lbs of food. Are you really carrying that much or do you have food drop or food cache?
Everyone's preference is different, but I have managed to plan my meals, so that they are eatable without cooking. Eliminating the need and weight for a stove, fuel, pots etc. that could save you 5 or more lbs easily.
I understand there is a psychological comfort factor with a hot meal. My intent is not to change your mind, simply share what works for me. Although most of SoCal you cannot have a camp fire without a permit... and they issue those in cold season.
instead of hot coffee in the morning, consider chocolate covered "gourmet" coffee beans. and if you are doing food drop or food cache, then perhaps those triple expresso thin tall cans, at least for the first day after the food cache.
consider a big variety and flavors of jerky: beef, turkey, buffalo.
Also, smoked salmon, salami, dry cured sausage, block of dry cheese, or laughing cow soft cheese that doesn't need refrigeration, as well as (pre) hardboiled eggs.
there's even chicken/tuna/spam singles in a foil pouch, ready to eat.
for starches: pretzels, crackers, bagels, bread buns, with those single servings of Smuckers jam, and Nutella hazelnut choc spread is also sold in single servings. if you take the single servings of Philadephia cream cheese, make sure you pre-freeze it, and consume it on your first day.
I'm sure you know about high caloric dense nuts that dont require cooking.
for the first 24 hours, I prepare in advance at home some cooked ground beef and mix it with cooked rice, then I vacuum seal (or use ziplock bag) and freeze it. by the time it thaws on day-2, its ready to eat with chopsticks straight out of the bag. I include those single servings of salt/pepper from fast food joints.
my personal preference is to stick with the katadyn filter, unless you know all the water in those 10 days is clean. Otherwise, a purification tablet does nothing for the muck and the mud. the filter is my one luxury item.
Also, if you get cold at night, a poorman's trick is to eat your high caloric big meal before bed time, because your body is like a furnace, feed it and it will keep you warm.
PS: break your toothbrush handle in half. Some guys here drill holes in the handle to shave ounces.
by the way, the swiss army knife is a cool idea, but I eventually realized I only need 2 or 3 things on it, and don't need a phillips screw driver, a bottle opener, that useless nail file, etc. I'd say plan to leave it at home, you already travel with a real knife.
There is a neat boyscout project to stuff as many survival items in an altoid tin http://www.youtube.com/watch?v=b6FzqB62JIE check it out, and if you have heavier duplicates, get rid of them.
you can also trim down your "lots of underwear" inventory. keep it simple: 1 to wear and 1 that you wash and air dry during the day. rotate.