I'm looking for manga (or anime, I guess), with protagonists who will go to most any lengths to accomplish their goals. That doesn't mean they might not have a few things they wouldn't do, but they shouldn't be very morally restricted.

Examples I can think of:
Death Note
Code Geass
Golgo 13
Shamo (although I hated that one)
Hellsing
Black Lagoon
Berserk might be an example
Teppuu would count. The protagonist isn't murderous, but is definitely ruthless in a more realistic sort of setting.

I'm betting I've read more, but I can't think of them at the moment. I generally like this type of character, but there doesn't seem to be a ton of stuff out there. If anyone has any suggestions, they would be appreciated!

Favorite Manga:
One Piece, Sexy Voice and Robo, Berserk, Teppuu, Hourou Musuko, Kekkaishi

This maybe?
I know it isn't exactly what you're looking for but there should be something to your likings (since some of your examples where mentioned in there.)

Hanzou no Mon
Lone Wolf and Cub
Samurai Executioner

Mirai Nikki
Fire Candy
Normal City
Elfen Lied

Edit:
Also perhaps A Certain Scientific Railgun. It's got a lighter tone than the others so it didn't come straight to mind, but Biribiri is pretty unrestrained when it comes to getting things done. I keep expecting her to have one of those 'I should be careful to be a good person and not kill anyone' moments, but she never does - just blasts everything apart at full power.

Code Breaker
Akagi

Battle Royale
Burning Hell

bolt from eatman
and maybe gunslinger girl

Samurai Deeper Kyo

[img]http://img545.imageshack.us/img545/9602/611839.jpg[/img]

Current Favorite:Seishun For-get!
Manga That Needs More Attention: S Senjou no Tena

Quote from Aikanaro

Edit:
Also perhaps A Certain Scientific Railgun. It's got a lighter tone than the others so it didn't come straight to mind, but Biribiri is pretty unrestrained when it comes to getting things done. I keep expecting her to have one of those 'I should be careful to be a good person and not kill anyone' moments, but she never does - just blasts everything apart at full power.

She doesn't. She's always in control when fighting other people and limits her power to non-lethal levels(or at least, to what she believes to be non-lethal against her opponent). She's definitely not ruthless at all, the only time she used her full power against a person she was literally in a berserker state and slowly going insane(and it didn't mean anything since her opponent was accelerator)

try shamo
bastard!!
or vagabond

Few people terrified me more than Dai, the protagonist of Let Dai... It's the sort of insidious, psychopathic ruthlessness that scares the bejeezus outta me.

Totally seconding Burning Hell. Those guys are so beyond ruthless that they're like another species or something... 😲

She doesn't. She's always in control when fighting other people and limits her power to non-lethal levels(or at least, to what she believes to be non-lethal against her opponent). She's definitely not ruthless at all, the only time she used her full power against a person she was literally in a berserker state and slowly going insane(and it didn't mean anything since her opponent was accelerator)

I don't buy that, given her railgunning of those thugs in the car and her repeated attempts to blast Touma with the expectation that it would hurt/kill him. Maybe 'ruthless' is the wrong word, but she's certainly reckless and has very little regard for the consequences. If she hasn't killed anyone (especially the car incident), it's only because the author is giving her a free ride.

I don't think Battle Royale is an example (probably a counter-example, unless you're considering the antagonists). I'll second Gunslinger Girl though.

i second Code Breaker
and add Kuroshitsuji perhaps?

** "It's so warm that, Before the snow has a chance to stick, He melts it for me." **

Oh, cool, lots of replies.

Some of these I actually have read, but there are a number I'll definitely want to check out. Thank you. More suggestions are still welcome, of course.

I added Teppuu to my OP list for anyone else who reads this topic. It's an MMA-centric manga that focuses on a ruthless female protagonist. She doesn't kill anyone, but that makes sense given the realistic setting.

Favorite Manga:
One Piece, Sexy Voice and Robo, Berserk, Teppuu, Hourou Musuko, Kekkaishi

Quote from Aikanaro

I don't buy that, given her railgunning of those thugs in the car and her repeated attempts to blast Touma with the expectation that it would hurt/kill him. Maybe 'ruthless' is the wrong word, but she's certainly reckless and has very little regard for the consequences. If she hasn't killed anyone (especially the car incident), it's only because the author is giving her a free ride.

She's not a killer and she's not capable of killing under normal circumstances. Yes, she is a bit reckless with her power, but she's always in control and careful about it, she never used what she considered as lethal force except against accelerator...

want proof? just check her fight with frenda(or simply read the index novels/railgun manga, it's pretty clear that she's literally nothing more than a normal middle schooler with an extremely powerful ability)...

Yureka The main character is pretty ruthless, he doesn't even think twice about hurting his friends, using them as shields and abandoning them when things get tough.