I recommend Private Internet Access:
1) Client software is always free, you only pay the subscription.
2) More than 2 dozen server proxies located in US, Canada, Western and Eastern Europe.
3) Accessible from within China (I've tried it, it works)
4) Supports Port Forwarding, UDP or TCP, and VPN Kill Switch (if you lose your VPN connection it will disconnect from the Internet).
5) Client software for both Windows and OS X, with manual setup instructions for tablets, phones (iOS, Android) and Linux, based on OpenVPN protocols, so you don't even have to use their client software if you don't want to, any VPN client that supports OpenVPN can be used, or you can setup manually yourself from within OS X or Windows.
6) Install client software on as many devices as you want, only limitation is no more than 5 can be logged in to any of their servers simultaneously, which I think is very generous.
7) Annual subscription is $39.95, price hasn't changed in three years.
8) they don't log or track usage, anonymous, especially if you choose a server in Canada or Europe where the laws are more pro-consumer regards the courts being able to request user data.
9) you can even purchase anonymously through various methods (gift cards, and so on), so there isn't even a paper trail back to you, and that is the main point right? Being anonymous.