Well, despite what you may think, you have probably already seen or heard of many popular Japanese Horror. However, you have probably seen the American versions. Dark Water, The Grudge series, The Ring series, One Missed Call, etc.
Here is my list of decent Asian Horror in no paticular order:
-Audition (As mentioned above)
-Battle Royale (Good book too)
-Films by Miike (ex. Imprint was alright)
You really need to have a weird sense to like these films. You need to realize that if you dont speak or understand Japanese, part of the thrill will be lost because you are reading subs. Even still, these movies are mostly just average to me. I still cant find a good supply of horror movies that engage me as much as I want them to.