"Tetsuo the iron man" and "Tetsuo II: body hammer" (if you can find 'em...)
"Sympathy for mr. Vengeance", "Old Boy", "Sympathy for lady Vengeance" (korean trilogy), "A Tale of Two Sisters"
"3-Iron", "Spring, Summer, Fall, Winter... and Spring"
"Violent cop", "Brother", "Hana-Bi", "Kikujiro"... Anything from Takeshi Kitano
"Wild Zero" for sheer awesomness
Classics as Battle Royale I & II, the Zatoichi movies, Akira Kurosawa, etc...