Walk along the west bank of the Gan river on a Saturday or Sunday and buy a cheap kite (Y10-30); join the hundreds of Chinese kite fliers. It's surprisingly fun.
Amusement parks - There is the Wanda Amusement Park in south Honggutan. There is also a smaller "fair" styled (but permanent) amusement park on the west bank of the Gan river (just south of the BaYi bridge in Honggutan). Here you can ride some surprisingly decent (and terrifying) rides, or try the dangerously-fast bumper cars for an awesome thrill and potential spinal injuries. You can also buy a wide variety of food at the outdoor food market, including stinky tofu and all assortments of chicken and icecream.
Bike - Buy a bike for ¥300 at Beijing Lu, ca 200 m off Ba Yi Square and discover the city on two wheels.
Hike and wander around the MeiLing mountains, west of the City. Consider checking out WanLi, a small town and gateway to fabulous hiking, biking, and other routes.
Rafting - At Meiling, there is a fantastic "white water rafting" course. It costs about ¥100, but is well-worth the cost. To get to it, you need to take a taxi or private van up through WanLi and still up, along a winding road and around the side of a hill town. The rafting place is at the end of a small road up there (talk to a local Chinese, who can search baidu for you). The rafting place has about 20 two-person inflatable rafts that bounce down the river (which has been artificially turned into a course with cemented rocks along the sides). Experience class 2 and 3 rapids, and have a lot of fun. You will likely not fall out of the rafts, but you will get soaked. Spend the extra ¥15 and get the "water guns" from the small shop, there. They add a whole new level to a group rafting outing, and are a hell of a lot of fun. Overall, highly recommended experience. Cost: ~¥120 per person, plus transport to/from rafting place.
Paintball, laser tag, and real CS - All across China you can find "real CS" which, although they'll tell you is paintball, is usually laser tag. There's a laser tag place under the Star of Nanchang Ferris Wheel. Some people think that's fun.
