ClarkTx,

I've never been to China, but I have done quite a bit of travel, in both the first and third world, and everything in between. Off the top of my head, here's some of the things I'd never be caught without on a long trip, or even a short one to a developing country (please note, I'm not a doctor, so check my med recommendations with one before you follow them!):

1) Notebook and Pen. You never know when you'll come across an amusing experience that you want to immortalize for the ages. Plus it gives you a may to preserve your thoughts and experiences when they are fresh, so that you can share them with us when you get back!
2) Purell. You've got that on your list already, but it's really helpful!
3) Pepto-Bismol. Take a dose if right after you eat something questionable, and it may help to avoid stomach troubles. The liquid is a pain to pack, but the pills or chewables are easy.
4) Benedryl. Works as an antihistamine for allergies (obviously) but also can double as a sleeping pill and anti-motion sickness med.
5) Ibuprofen. My favorite OTC painkiller. Taking it with you sure beats trying to find it locally when you need it (I have a funny story about trying to buy naproxen in an Australian pharmacy when I had severe back pain. It would have been much easier if I'd brought some from home!). The stress of changing timezones, lack of sleep, foreign culture, etc. can often lead to a headache, in additional to the regular muscle aches of spending all day on my feet as a tourist.
6) Codeine. I'm sure that this will be controversial to some, but I have found it to be very useful. It works as a painkiller when ibuprofen is not enough, but also as a cough suppressant and anti-diarrheal as well. Be careful to have a good prescription when crossing borders.
7) Cipro. Probably overused, but all the research I did shows that it does help against stomach bugs picked up through food.
8) Immodium. Already on your list. The few times I've needed to use it, it's always been quite unpleasant. If you've got the time and access to clean water, letting traveler's diarrhea run it's course is probably a better option.
9) Oral rehydration salts. These come in a compact packet, and if the pepto, cipro, and immodium don’t work, can make the difference between an unpleasant time and a trip to the (questionable) hospital. Always seemed like cheap insurance to me and really helped out a companion once.
10) Pocket-sized camera. I love my digital SLR, but the best photos often show up when I don't want to lug it around.
11) A sense of humor. VERY IMPORTANT!

A final tip I've found very useful when traveling in countries where I not only don’t speak the language but can't even read the writing: Have your hotel/guesthouse write down its name and address in local characters on a card for you. If you need to, you can just hand the card to a taxi driver and he should be able to figure out where to take you, even if you can't otherwise communicate.

There's a lot more travel advice in my head, but this is too long already. Have a great trip!