Light and L of Death Note shout "I AM JUSTICE!" and variations ("Justice will prevail", "I have become Justice," etc.)... and it is thoroughly deconstructed.
Kazemakase Tsukikage Ran: Meow will fight anyone for this reason. She even calls herself 'The Beauty of Justice'
The World Government Marines in One Piece have a bit of a thing for justice. Aside from having the characters for justice printed on captain-rank officer's coats, several prominent personnel tend to have their own take on the concept; Admiral Aokiji has "Lazy Justice," Admiral Akainu has "Absolute Justice,"Rob Lucci has "Dark Justice," etc.
Superman is actually a subversion of this though. He's mainly concerned with For Happiness, spending most of his time doing random acts of kindness like stopping floods, chasing off supervillains, and plucking kittens out of trees. He doesn't much care what supervillains do as long as they're not hurting anyone (or being Lex Luthor). Writers have him bandy the term "justice" around a lot, but crimefighters like Batman and The Flash are a lot more focused on criminal justice than Superman is.
In PS238, an elementary school for the children of superheroes (and villains), some of the superkids have gotten an odd habit:
Kid #1:"To the cafeteria!"
Rest of the class: "FOR JUSTICE!"
The much criticized Justice League: Cry For Justice has a lot of the characters saying that they "Want Justice!" despite the fact that they are really just out for revenge.
While the X-men have a somewhat more original concept, and had some of the first antivillains in American comics, the promos for the cartoons would talk about using mutant powers "for the benefit of mankind."
Judge Dredd. While he can often come across as an uncompromising jerk, people too often forget that the Judge really does embody the Lawful half of Lawful Neutral, and his primary motivation in doing so, is his conviction that his society will not survive without it.
Film
In Star Wars, Obi-Wan described the Jedi as "the guardians of peace and justice". Of course, he was talking to a young-for-his-age twenty-ish rube with stars in his eyes.
In the opening scene of The Godfather, we see a very affected Amerigo Bonasera explain how, for justice, he must go to Don Corleone.
Literature
This is the driving force behind the Knights of the Cross in The Dresden Files. No matter what their background, the Knights are driven by the sole purpose of righting wrongs, fighting evil, and protecting the innocent. In a setting that at best runs on Grey and Gray Morality, they are unquestionably the Good Guys.
“Consider the guilty person who comes under your jurisdiction as a poor wretch, subject to the frailty of our depraved nature, and insofar as you can, without doing harm to the prosecution, show yourself to be pious and clement, because, although the attributes of God are equal, mercy flourishes and is more resplendent than justice."
Live Action TV
Angel. "We live as though the world is as it should be, in order to show it what it can be." Angel initially thinks that he does what he does, in order to gain redemption and avoid going to Hell; but he eventually realizes that he helps people simply because doing the right thing is an inherent part of his identity.
Odo in Star Trek: Deep Space Nine was motivated by what he described as an inborn need for justice. Law was a secondary thing. He used to theorize that a need for justice may have been an inborn trait of his unknown species...too bad it turned out not to be the case.
Their natural tendency is only to enforce order and obedience. While Odo justifies the need for both with Justice (no pun intended), the rest of the species is only interested in domination (ostensibly to protect themselves from ever being victims again). Odo's experience working as chief of security under the Cardassians, witnessing the atrocities and the oppression of the innocent Bajorans, is implied to have taught him the value of Justice over pure order. He still takes the Lawful part of Lawful Good very seriously though (so long as the Law in question is itself "Good", like when he allowed several Cardassian dissidents to escape because their crimes did not warrant the death penalty they would have received otherwise).
As do the Tau Empire in Warhammer 40,000, with their ubiquitous catchphrase, "For the Greater Good!" This has the effect of making newcomers to the series believe and latch onto the idea that the Tau are the "Good Guys", prompting others to mock them with the phrase "Good for the Good God!"
The Tau were this in their original incarnation. At first, the Tau were a Mary Suetopia whose White morality clashed terribly with the setting's charcoal-grey-on-black-on-event-horizon-of-a-black-hole morality. Fan reaction was fairly negative. The Tau got a bit of character development and started doing things that would make them Scary Dogmatic Aliens in most settings, but by 40k's absurd Stealth Parody standards, the Tau are downright nice guys. The Tau may not be in it For Great Justice, but they're amongst the least evil. By now, the Tau have been accepted by most of the fandom. However, the fanbase is so broken and vocal that everything is hated by a good chunk of the fanbase.
In Mega Man Battle Network 6, the Joke program causes MegaMan.EXE to lampshade this line during a joke. When that fails, he tries to one-up it into "For Greater Justice?" Lan is not amused.
Probably the most common character trait found in hero profiles in JRPGs. It isn't unusual to find an entire team of characters with no similarities apart from having "a strong sense of justice."
Although in Tales Of Symphonia and its sequel it's subverted somewhat, in that Lloyd realizes it's a Meaningless Meaningful Word and doesn't resort to just calling it out as a motivator (and gets pissed if someone else does, particularly when used by Well Intentioned Extremists like the Big Bad for both games).
And completely inverted in Star Ocean 3, when the in the gap between the penultimate and ultimate battle, the Big BadLuther's world comes crashing around him and he goes rather mad. In a rather Narmy fashion, he screeches at the party that "RIGHTEOUSNESS SHALL PREVAIL!" before attacking.
DeathSpank is a self-described Dispenser of Justice.
Tsubaki gets in on this in BlazBlue. She's a fan of historical dramas, and in the "Help Me, Professor Kokonoe!" segements, it's shown that it's the source for her battle quotes.
Her achievement/trophy is actually named after this trope.
Linkara's review of Justice League: Cry For Justice issues 3 and 4 has him beginning the review with the inevitable joke of, "So, let's review issues 3 and 4 of Justice League: Cry For Justice. For Great Justice."
