for quite some time I had heard all this great commotion (internet and beyond) over a japanese horror movie called Junk. I found it at a blockbuster music store that was closing down. I waited for them to get really close to going out of business (cos' that's when the prices are really good) and I bought it for 10 dollars versus the 28.99 they wanted for it in the beginning. I love good terrible movies (see, Troma). but, this one is definitely in a world of it's own. it's portrayal of the yakuza is just as good as it's protrayal of the living dead. though there is one great scene with a scientist sharing a snack with one of his nurses.

battle royale series. great

it's not a horror film but it's very violent and disturbing either way:
Ichi the Killer, avoid the cheaply made prequel Ichi 1 though.