The Clans from Battletech suffer from this when they invade the Inner Sphere. One of the biggest reason for their failure is that the Inner Sphere refuses to fight to the Clans' rules, and actually takes advantage of the Clans' adherence to their code. Example: Clans traditionally begin battles with a challenge that states how many troops they are committing to the assault, and asks the enemy what they're preparing to defend with (this actually makes sense for inter-Clan warfare; they're short on resources, so they want to keep battles small so as to minimize casualties and collateral damage). The Inner Sphere, of course, would lie. Later averted by most Clanners, who simply come to the conclusion that anyone who doesn't want to fight by the rules shouldn't be protected by them.
Another reason of they failure lays in the fact that they must quantify their honor. For the Clans honor is not an abstract concept, they were created by a Proud Warrior Race Guy. When preparing for combat they will enter into bidding rounds and the lowest bidder will have the honor of proving that they bid exacly the right ammount of troops needed to win the battle. Clans defy reason when their commanders will willingly bid lower than the minimum number of troops needed to win the combat, and that according to Clan estimates!
Warhammer 40000: Space Marines generally eschew camouflage in favor of wearing distinctively-colored armor, and often have troops whose primary purpose is to bear banners conferring only psychological advantages.
This is more an aesthetic choice: Space Marines are in part analogues to knightly orders and warrior brotherhoods of old, and they're awesome enough warriors that camouflage isn't really a big deal. A better example would be times where a squad, company, or even entire Chapter of Space Marines go up against overwhelming odds to recover some sacred relic of their Chapter, which may very well be nothing more than a tattered old banner.
While it is an aesthetic choice, it is noted that the Ultramarines, whose codex tends to be the rules Space Marines go by, consider stealth and indirect warfare cowardly, which contributed badly to the Horus Heresy when their Primarch Roboute Guilliman refused to acknowledge his brother-primarch Alpharius for his brilliant and flexible combination of adaptive military combat and undermining the enemy from within even when Alpharius went to extreme lengths to prove that his methods were worthy because he judged Alpharius's deviation from the rigid outlines of the already established doctorines dishonorable. This would come back to bite Guilliman later when the Alpha Legion turned traitor because Horus was one of the only primarchs who appreciated them, and underestimating their adaptable tactics cost the Ultramarines dearly in combat and allowed the Alpha Legion to continue to operate with impunity within the Imperium.
The Horus Heresy novel 'Know No Fear' shows us Guilliman's real problem with the Alpha Legion isn't so much that they were dishonorable, but that their thinking was inferior. Guilliman preferred strict structure and fighting enemy combatants, while Alpharius taught his Legion to favor unstructured combat and command; to attack from within, and to not limit their targeting to military targets. While in the 41st millennium Guilliman's attitude seems silly, it made a lot of sense in the 31st millennium - It had made the Ultramarines the uncontested, most successful Space Marine legion of the Crusade, taking more planets then any other. In addition, their straight, honorable combat often made integrating whoever the conquered into the Imperium far smoother and easier due to the respect of their defeated foes. The Alpha Legion tended to leave planets confused, decimated, and all together very, very unhappy with them. It should be noted, however, that the Alpha Legion did not turn to Chaos over this minor spat - It's just why the current Ultramarines think they did. Which is more of a Pride Before Reason problem.
The still-really-popular Marvel Superheroes RPG had this as a game mechanic. You couldn't use use Mind Controlin any circumstance without losing Karma unless you were a villain. The idea being, of course, that the GM should always include a way to win without removing a person's free will. This was a superhero game, after all!
The godess Rondra and her church of the pen & paper RPG The Dark Eye are a fine example of this trope: Over the course of time Rondra degenerated from a goddess of war into a goddess of honor, going so far as to deem battles between armies and the art of war (strategy and tactics, that is) as "necessary evils" and only approving of one-on-one combats, which meet certain standards of honorable behavior. This development hasn't been without consequences in the game world itself: it has been mentioned that army officiers tend to worship Hesinde (a godess of knowledge) or Phex (a trickster god of luck and wits) instead of Rondra. Not to mention Kor, a merciless god of bloodshed and mercenaries, who has a considerable amount of followers amongdisillusionedwarriors. And it seems as if yet another god prepares to compete with Rondra and take over her old domain: Nandus, a god of reason, whose followers unsurprisingly prefer reason over honor.
High Compassion and Valor virtues in Exalted can create an ersatz form of this trope.
Virtues work this way in Scion. If a character wants to go against what their virtues would compel them to do they need to make a dice roll and fail to take the action, for example a character with Courage would have to fail a Courage roll to pass up on a fight with a dangerous opponent or willingly accept help from another person. If a Scion ignores their virtues too much they succumb to the virtue extremity and act out the extreme of the virtue.
The Adamantine Arrow of Mage The Awakening have the importance of honour enshrined in their creed as "Enlightenment is Honour". The Arrow believe that oaths are a deep expression of one's soul, and that fighting without honour is meaningless, so when they give their word they take it very seriously. That said, they are still encouraged to consider a situation carefully before committing themselves to anything, that their oaths should be simple and state exactly what they intend, as well as accounting for all possibilities (for example "I will be dead before you have this grimoire" is considered less preferable to "I will be dead before the enemy has this grimoire" since the former doesn't account for former enemies becoming allies). Overall, while they should keep to their word and their code, they should be careful not to cripple themselves with it.
One of the three Renown categories from Werewolf The Apocalypse is honour, which is often associated with the law-keeper Philodox and 'just' deeds.
It becomes one of five Renown categories in Werewolf: The Forsaken, where it's associated with the Philodox-equivalents, the Elodoth.
In Traveller there are several variations of this for different cultures. The Fteirle code of the Aslan is highly developed as befits a Proud Warrior Race.
Dwarves in Warhammer Fantasy are this trope's posterboys. If they have some great dishonor that befalls them, sometimes as minor as not keeping a promise or a young dwarf being turned down by the girl they fancy, to something as major as kinslaying or failing to stop an assault on a stronghold, they lose the will to live. However Dwarves physically and psychologically find it impossible to commit suicide, so they become slayers and go fight the biggest baddest thing they can find until they find one that can kill them (they never fight to lose either).
This is a major problem in the Gotrek And Felix series; a Slayer's shame will not be relieved until death, but Gotrek seems to be completely unbeatable. Another is that the shame must be foremost on their mind when they die to relieve it, and Snorri, another slayer, has taken a lot of blows to the head over his career as a slayer and can't remember what it was.