Ultra-violent Anime.

[AngelicSven]

Hellsing has been said but i will reiterate it.

[b/]Watch Hellsing Ultimate if you want awesome gory violence!!![/b]

Yep, I haven't someone grind an immortal's face onto a wall till it was complete nothingness in any other anime.

Also, Elfin Lied, Gantz, Darker than Black, Higurashi...

 

[Verp]

Genocyber

Shigurui

No seriously, bloodshed is pretty much the only thing that Shigurui has going for itself and I must admit that it does it pretty interestingly.

Edit: Oh yeah, Kemonozume is pretty violent too, in addition to being strange as hell.

 

[Scarim Coral]

Oh god don't remind me of Genocyber. I was young when I watched that and it pretty much traumatise me, well it wasn't bad but I did felt pale watching it.

 

[Semi-Human]

Personaly if its just ultra violent a show starts boring the shit out off me though.

Elfen Lied okay i guess

Hellsing, Gantz, ninja scrolls are good. So's berserk but a little old. Neo genesis and Akira both have there moments. Shiguriu is ultra violent but sucks as a story.
You might wanna try Ichi the killer the anime

 

[Shadow-Phoenix]

Evangelion
Fist of the north star ( come on guys that literally explode when Kenshiro taps them)
Hellsing ultimate
Higurashi
Elfen lied
High school of the dead

There are a lot more but thats all on my mind right now.