Oh, well I can't say I've heard of it. :P
Elfen Lied
Berserk
Wicked City
Baoh
Ninja Scroll
Genocyber
Urotsukidōji
X
Hellsing
Psycho Diver
Twilight of the Dark Master
Blood: The Last Vampire
Angel Cop
Gantz
All of the above are 15/18. Anime is treated just like films and video games, why should it be treated differently just because its animated? Thats funny actually, video games are animated and no one says they're for kids and don't have 18 ratings. There are even animes with R ratings.
Would you like to see some pictures form the animes above? ;)
I can find a lot more if you want. ;)
I rest my case.