He points Levy at stuff.

He makes himself useful, but in a discreet kind of way that's not often onscreen. He talks to people. Negotiates.

BotS isn't actually that bloody. (Though the bit about "We don't have the men or material to help you with peacekeeping. We do pack planet destroying bombs, though." did happen.)

As for Black Lagoon - the protagonist never actually learns to fight. But it's not about him. And he does get more and more tainted by the killing around him.

Black Lagoon's all I can think of right now. Heroic sociopaths at work. With guns.

Also, the Crest and Banner of the Stars series has basically decent protagonists, who happen to serve in a galaxy conquering army whose idea of peace keeping is "Solve this by yourselves or we blow up your planet".

Oh, and the Slayers. A classic.

What genre? What have you already watched?