Slasher anime

[pianocello]

I'm making a listing of anime that's similar to Hollywood slasher movies such as Prom Night, Urban Legend, Halloween, Friday the 13th, I Know What You Did Last Summer, etc. Usually in these shows, there's some mysterious killer (whose identity may or may not be a mystery) who goes round killing a bunch of people (usually a bunch of horny youngsters). It may be the standard hack-and-slash or perhaps even killing in more creative ways. There is usually an air of mystery in the show.

I'm NOT talking about detective anime like Detective Conan or Kindaichi. Rather, the few examples that I can think of that comes closest to matching these criteria are:

Perfect Blue
Higurashi ~ When They Cry

Are there any others that I may have overlooked?

[Fencedude]

Elfen Lied

[Yukino Miyazawa]

Chaos;HEAd (http://www.animenewsnetwork.com/encyclopedia/anime.php?id=10182)
Kara no Kyoukai (http://www.animenewsnetwork.com/encyclopedia/anime.php?id=7472)
When They Cry 3 (http://www.animenewsnetwork.com/encyclopedia/anime.php?id=10168)

[One Vorlon]

Requiem from the Darkness and Hell Girl are very similar to the Nightmare on Elm Street movies - supernatural entities hunt down people and trap them in their own private pocket of hell.

Paranoia Agent is all about the hunt for Li'l Slugger.

And don't forget Boogiepop Phantom, which has both a serial killer and the Angel of Death stalking the streets.

There are also a couple of other shows that aren't quite as good a match - Fullmetal Alchemist, for example, has Scar (who's using alchemy to explode people's skulls) - but he's not really the main focus of the show. And Betterman features a condition where people suddenly flip out and go psycho killer - and there are several episodes which fit the "slasher flick" rules.