My favorite thing in Shenzhen is bargaining for electronics at Huaqiangbei, it feels like going to Disneyland. Over millions of square feet, merchants sell stuff from wires, LEDs and transistors to headphones, monitors and hard-drives. I used to pay electronics for 80% of their value, then I learned Mandarin and got them for 40%. Definitely try learning numbers in Mandarin and work on your poker face before getting your plane ticket.