I travel to China almost every year during the summer so I guess I know a thing or two about the country.
Let's see, first thing, a microfilter might not really be necessary, after all you are only going to be there for two weeks in a large city, and bottled water is so cheap there (you can buy several liters for a dollar or so at large supermarkets). Otherwise you can always cook a lot of water the evening before and let it cool over night, it's what the locals do. The place you are staying might even have a water cooler, and a refill costs even less per liter and is almost always delivered to your door. A water filter would most likely just mean extra weight that you can't use to carry stuff back.
Someone on Equipped mentioned that you probably shouldn't bring fancy lights. I've been to China several times with an Arc4 and Arc AA, and it has been no problem at all, and might come in handy, as some large cities have electricity shortages with a few blackouts each summer (then again you could just buy candles there). Just make sure you don't loose your expensive light. AA batteries are really dirt cheap there, and cr123's (not always genuine brand name ones mind you)cost about a dollar a piece in eletronic markets (if you can haggle). Again don't bring anything you would really really really mind loosing, or just don't loose anything (goes for everything else really).
Bring deodorants. It will be warm where you are going, even well into the September or even later. In Beijing, and other northern cities I've been to it has been impossible to locate any deodorants except in really trendy and exclusive supermarkets for westerners, and there they cost quite a bit. Then again it's probably easier when you are close to HK. Or you can just smell like everyone else there. If you are a woman (can't see from your username can I?) or travelling with female friends, then you should definitely bring female hygiene products, as some of them are rare and others are of a bit dodgy quality (or so I've been told).
A good little knife could be great too for all the cutting chore and more. I had a Strider AR with me a couple of times, but have never used it, ever. Instead I used my single-blades SAK the most. So a small, non-dangerous-looking and cheap Spyderco or Benchmade (mini grip?) or SAK will be best in my experience (unless of course if you travel to the country side). As a foreigner you can probably get away with a lot, but the usual caution with knives applies here, i.e. be discret and find out where you can carry it, as it would really suck to have your favourite confiscated because some policeman saw it and fancied it himself (again being a foreigner would help a lot so don't worry too much). A multitool could be good too but if you are going to be in a city for two weeks I really don't know what to use it for.
Bring a money belt or a similar thing so you can have the cash and papers you don't need in there.
A first aid kit with all the medicine you use (and things like sunscreen, which is a bit diffcult to find) could be good too. You certainly can almost find everything at a good drug store, but again I wouldn't try buying them if I don't speak the language.
A cheap and good watch could be useful too. Wearing expensive watches are just asking for trouble, and in general don't try to show your wealth on the street, try to blend in. And southern China is like the counterfeit watch capital of the world, so you might pick up something cheap and cheerful there.
Oh and bring a bandana or or small towel so you can wipe the sweat off of your face.
Good English books are hard to find and expensive, so bring some good pocket books that you can just throw away when you leave. And although even non-pirate CD's are cheap (less than ten dollars if you dig a bit) but don't count on finding every band, so bring your own if you have too.
Most of the things you don't actually have to carry with you, personally I leave quite a bit at where I live. But then again I I don't EDC much in general, especially in cities, so you can take it with a shaker of salt if you like to carry more.
Just what I can think of now, but feel free to ask questions.