All of Hunan has spicy food, but the Tujia minority in Zhangjiajie seem to use it the most. Every dish has some hot peppers. The foods great but will get you in the end.
Hunanese people like their food spicy and everything is served up with plenty of red chili. Mao Zedong once suggested that the Hunan peoples' rebelliousness could be put down to the fiery red food that they ate! Unlike other parts of China, where you will usually be asked how much spice you want, in Hunan it is always assumed that everyone eats their food at its firiest level. If you don't like the fiery furnace sensation when eating, let the staff know at the outset!