[Rin, Pyo, Tou, Sha, Kai, Jin, Retsu, Zai, Zen]
Kuji, or the Nine Syllables, are a part of a lot of ninja pop-culture. Anime, live action movies, video games, they all tend to use this a lot. The syllables themselves are usually recited together with hand motions, called the kuji-in, or nine syllables seal, or with alternating horizontal and vertical slashing motions, the kuji-kiri or nine syllables cut. Ninja use them as a way to prepare themselves for some difficult task, both as a way to focus/calm, and a way to increase power/luck.
Well, luckily, Wikipedia has a good rundown of them. Also, if you want to try to make the kuji-in yourself and impress your friends with your mad ninja skillz, check this out (read from top right down).