A lot of good suggestions here, some of which don't fit the OP's description but are perhaps worth branching out.

Some examples that haven't been mentioned that fit darker action oriented anime to varying degrees:
The Big O
Gunslinger Girl (preferably the first season)
Parasite Dolls
Armitage III
Key the Metal Idol
Silent Mobius
Wolf's Rain
Requiem from the Darkness
Mononoke
Now and Then, Here and There
RahXephon

I am busy... sooooo busy. No time left at all.

Seriously, this really helped. It is tough to look at a wall of ambiguous titles and know what to watch. If I do stumble upon one that doesn't include the Big 3 then I will have to revisit this for that prize.

I should really thank Pokemon for first introducing me to anime.
Thank you, Pokemon.

What I saw of Gantz was gritty but not very action packed. Most of the action kept pausing so we could listen to the thoughts of every single person involved. But none of my ideas were very gritty, so I don't mean to second guess your recommendation.

Not really watched any since the late 90s but some of my favourites were:

Akira
Vampire Hunter D
Ninja Scroll
Guyver series
Golgo 13

And the one that has stuck with me and still gets watched every now and then Oedo Cyber City 808. Great childhood favourite of mine.

http://www.youtube.com/watch?v=BlZakDfseyo

It's a bit old now, but Last Exile is a classic, one of those epics in the great tradition of Escaflowne.


As for where to watch, I am not a fan of streaming sites because its so LQ. Get the 1080p/720p BR versions... Google is your friend.

I personally would NOT recommend Akira. At all. Sure, it's a great story, but the movie butchers it. The manga version is huge, and the movie tries to pack it all in. The last 30 minutes of the movie is an utter trainwreck loaded with plotholes and "wtf just happened" moments. Sure it looks spectacular for an 80s movie, but it's just not that good. I'm surprised that it's hailed as the best anime movie of all time. However, if you enjoyed the lifeless feeling of the first Ghost in The Shell movie, you would probably love this one. I like Ghost in The Shell, but the first movie is just not that good to me. GITS 2: Innocence was much better IMO, as well as the tv series.

I would recommend Fairy Tail

I recommend Neon Genesis Evangelion. The best anime ever made imo.

Failing that Elfin Leid is good.

I'd recommend...

Movies:
Sword of the Stranger
Blood: The Last Vampire
Nausicaa of the Valley of the Wind

Series:
Galaxy Express 999
Xam'd Lost Memories
Hajime no Ippo
Michiko to Hatchin

Watch this one. My favorite.

And anything Studio Ghibli related is a great watch.
At least I know someone else has great taste on here.

Outlaw star!

i always recommend fist of the north star
aside from the two tv series dvd boxes that still come out i have everything on dvd, but i still havent seen everything
the movie from 86 is great, but you wont unbderstand much of the story, but by the end of the day you have seen a lot of gory fighting
the tv series from 84 is also great

its basically about some martial artist in the post apocalyptic world, he looks like stallone, dresses like mad max, and behves like bruce lee, also: head explosions!

Oh cows!

And Wangan midnight the anime series :D

One of the best anime's i have watched, Prolly not what your looking for though :E

legend of the overfiend?

;)

has anyone suggested the Macross stuff?

specifically Macross Plus, Macross Zero, and Macross Frontier?

(zero and frontier you will probably have to torrent, cause they are simply NOT for sale in the EU & US .... licensing issues)

just stay away from the Super Dimensional Fortress: Macross & Macross 7 as those two take a special type of fan to endure in this day and age.

additionally you can try out Gundam, most all of them are exceptional but much like SDF: Macross and Macross 7 tv series, many of the Gundam TV series are quite hard to sit through for various reasons (old animation, too much filler, depressing ass plotlines, etc ...).

the main three highlits that everyone should watch are 0080: war in the pocket, 0083: Stardust Memory, and the 8th MS team.

one of my personal favorites is Gundam F91, but G-Fighter is really entertaining in it's own special way, and Gundam IGLOO (yes another weird name for a great series) has got some of the most mature (as in "not porno" type "mature") story lines I have ever watched.

other than that I highly suggest Turn "A" Gundam (despite it's weird look at first glance it's actually one of the best gundam series and the true "end" to the Gundam continuum before Bandai turned the series into a Yaoi drama).

Gundam Unicorn is currently in ongoing production right now, but Bandai is charging way too much for the BRs (like $50 for one episode per disk) although you can rent them off the PSN for a little less.

Oh so many choices,

Darker than Black

Phantom - Requiem for the Phantom

Valkyria Chronicles

Sengoku Basara (A show based on historic events, BUT they have given the main characters SUPER powers, Good for a laugh, and well in the battles in this show, there are no such things as ambushes, its head on fighting).

Metantei Conan/Detective Conan/Case Closed a longrunning detective series, If you can get by the mainpart of the story, a 16-17 year old detective poisoned by a poison that would normally kill and remove any trace of the body, just turn him to a 6? year old, that still solves bloody murders and other cases, it is quite good.

Onmyou Taisenki

Shonen Onmyouji

Busou Renkin

Chrno Crusade (Well, might not be a to good fit, but its a good one)

Inukami! (Ok, this one might remove any remaining sanity in anyone who watches it, And you will not be able to look at an elephant and not snicker at a memory from this show).

Think ill stop here.. ;)