They say that Sichuan food is the best in all of China, and that Chongqing noodles are the tastiest. It's certainly a fun rumor to try and validate.
These are Chongqing hot and sour sweet potato noodles, 酸辣粉. The noodles are made from sweet potato flour, so they're gluten-free. They come with crunchy salted soybeans and loads of Sichuan pepper. You can buy them at every little street food cluster at night, and even at a lot of convenience stores. Hao You Lai Restaurant is pretty good, and is near Liberation Square.