Travel to Canton Fair and sight seeing. Do I need a special visa?

You'd better apply for a L visa for tourism. So, don't mention visiting Canton Fair in the application form. If you do, you have to provide invitation letter from the organizer or a company to apply for F business visa instead. For L application, you need to provide your passport, application form, one recently taken 2X2 inch photo, the latest 3 months bank-statements with adequate money, hotel reservation in China and round-trip ticket booking.