Hitokiri (which translates roughly as "assassination"), a/k/a "Tenchu" which translates roughly as "divine punishment") showcases Hideo Gosha at the top of his form. Do NOT miss this one, or Gosha's other classic, Goyokin! Hitokiri is not only one of Gosha's best films, it's one of the best "samurai/chambara" films ever made, and perhaps one of the best Japanese films ever exported.
Be warned, all of the intricate plot details in Hitokiri can be a little hard to follow for those unfamiliar with 19th century Japanese history. Even so, the underlying human drama is obvious and open to all viewers. As per the norm for Gosha, Hitokiri provides yet another variation on his traditional theme of "loyalty to one's lord" vs. "doing the right thing". However, Gosha develops his favorite theme with such sophistication, that it's really _the_ movie to see (along with Goyokin, of course).
I suppose it breaks down like this: If you want a simpler, more action-oriented tale, you might want to see Goyokin. However, if you want a more thoughtful, multilayered (albeit grim) drama, see this one.
(OK, OK, essentially, the historical backdrop is a massive power grap between many different samurai clans who are either (1) working to reform, yet retain, the Tokugawa Shogunate, and (2) those who are trying to install the Emperor Meiji as the supreme ruler of Japan. Of course, those clans working "for" Emperor Meiji were often less interested in "reforming" Japan than in ensuring their own clan more power in the "new world order". Ironically, the entire feudal system was officially abolished as one of the first reforms of the Meiji government. It's ironic twists like this -- Gosha's big on irony -- that make the entire plot all the more bittersweet.)
What distinguishes "Hitokiri" from Gosha's other movies is Gosha's mature sense of cinematography. Every shot is thoughtfully composed, and (much like Kubrick's Barry Lyndon) each frame of the movie could hold its own as a still composition. Of course, this is typical Gosha. Hitokiri really stands out with stunning backdrops, including(as with Goyokin) many riveting seascapes. Just watch the opening sequence, and you're hooked! Make no mistake, this is no English period piece: Hitokiri is extremely violent (don't say you weren't warned).
What else, other than cool camera work, makes Hitokiri stand out? The performances seem (to me) a bit more subtle in this one. Katsu Shintaro (of Zatoichi/Hanzo the Razor fame) turns in a star performance as the conflicted protagonist/antihero, Okada Izo. Katsu manages to instill humanity to a character that seems almost more wild animal than villain. Throughout the movie, you're never quite sure if you're engaged or revolted by Okada's character. At the same time, Katsu's portrayal of Okada's ravenous hunger for respect, and his later pathetic attempts at redemption, seem so human that you can't help but feel empathy/sympathy. Of course, after seeing Nakadai Tatsuya play the tortured hero in "Goyokin", it's great to see him play such a ruthless villain in "Hitokiri". He's just perfect, there's nothing more to say!
As a final note, perhaps more interesting to buffs than to casual fans, don't miss the last screen appearance of Mishima Yukio (yes, the closeted gay right-wing ultranationalist novelist who committed suicide by seppuku before the crowd of jeering Japanese military personnel he "kidnapped" in 1970, and had a movie on his life and work made by Paul Schrader), who actually does a pretty solid job of portraying the honorable (for an assassin) Shinbei Tanaka.