Related to Mook Chivalry, except it applies to all villains. The villains will never go for a sneak attack that is really any good. Some things include:
Killing the hero when he's asleep is dishonorable — A villain would never have the common sense to simply sneak (or teleport) up to the hero while he's asleep. Common sense would tell you that a villain could easily win by waiting until the hero is asleep and then killing him.
I must never attack from behind without some sort of warning sound — It never occurs to villains to sneak up behind the hero and blast him into oblivion on what is supposed to be a normal day when the hero is off guard. If the villain attempts to attack from behind, he will always make some sort of noise, like a yell, to warn the hero to dodge or be pushed out of the way.
- Ah! My Goddess: Mara, the demonness and arch rival to the goddesses, has demonstrated an ability to seal away Belldandy and/or her powers. It never occurs to Mara to sneak in at night or sneak up from behind and do this.
- Happens twice in Code Geass: both when Nina tries (repeatedly) to kill Zero (yelling "Euphemia's revenge!!" incessantly), and when some Britannian soldier tries to assassinate Suzaku, the latter of which would have worked if it weren't for Suzaku's "Live on!"
- Also, Suzaku's attempt to kill Charles, which involves charging in like an idiot and making a long speech about crimes and despair and whatnot. There's some sadly unexplored hilarity in the fact that Charles was invulnerable by that point.
- Averted at the beginning of the "Magical World" arc in Mahou Sensei Negima!: Negi and his group arrive at a Gateport coincidentally at exactly the same time Fate Averruncus and his group do. Fate is initially willing to let Negi leave without noticing him, but when Negi begins to detect his presence, he impales Negi out of nowhere with a giant stone spear. Only by the timely actions of the other heroes does Negi barely escape death.
- In Fate/stay night and other related works, this is justified when it comes to the Assassin class of Servants. Being in an RPG-Mechanics Verse, Assassins have a trait known as Presence Concealment, which allows their mana signature to become undetectable even to other Servants, allowing them to sneak around and scout in enemy territory. However, the efficiency of Presence Concealment almost always plummets whenever the Assassin prepares to go for a sneak attack, allowing the target to deflect or avoid the attack quickly enough. It isn't much of a problem against normal humans, given how Servants have Super Speed and can kill them the moment they register that they're being attacked, but this also makes performing sneak attacks against other Servants practically worthless. And since the Masters of the Grail War often like to keep their Servants by their side as an invisible Guardian Entity, it's not easy at all for an Assassin to get the drop on other Masters.
- In The Cabinet of Dr. Caligari, violating this trope is Cesare's job. And if you think it's unfair that he kills you in your sleep, don't worry: he kills you in his sleep, too.
- The Assassin's Guild in Discworld has explicitly defined standards as to how one is permitted to inhume a client. These standards permit Commander Vimes to set up defenses around his home and office to ward them off. He gets so good at humiliating would-be assassins thanks to this trope (and so vital to the day-to-day running of the city) that they eventually stop accepting contracts for him, and instead use his defences as a test. No, not killing him, just getting to where one can draw a bead on him is considered exceptional.
- Averted in The Lord of the Rings, when Sauron does send his Ring Wraiths to attack the heroes while they sleep in the town of Bree. For most of the rest of the story, our heroes are either traveling under Sauron's radar, shacking up in well-fortified areas he can't sneak into, or pulling off elaborate distractions to keep him from zeroing in on where the ring is so he can't try this again.
- In A Song of Ice and Fire there's an order of assassins who always apologize to their victims before killing them. This is a whispered "Sorry," an instant before death, but it was enough warning for one character to avoid it.
- In the Dragaera novels, one of the rules the Jhereg follow is that you cannot assassinate a target in their home. If they step one foot outside the front door? Fine. One step inside the threshold? Safe.
- Justified in Mighty Morphin' Power Rangers: Rita could only get rid of the Rangers if she killed them while they were morphed; otherwise their powers could just be given to another person. Lothor would later invoke the same rule in Power Rangers Ninja Storm.
- In Charmed, demons have the ability to teleport in and try to kill the Charmed Ones, seemingly at will. While they do take advantage of this, they always do it when they're awake, usually in the same room, and not occupied with anything else. The idea of doing it while they're asleep doesn't seem to occur.
- Encouraged as protocol for the Keeper in the Call of Cthulhu core rulebook. As the Investigators tend to be mere Puny Earthlings, devouring them in their sleep or when they otherwise can't fight back tends to be boring and anticlimactic. Individual pre-written adventure modules may play this straight or avert it, however.
- Subverted in the Forgotten Realms setting, where the assassin Entreri often does kill people by sneak attacks, and on one occasion when he does cry out when attacking someone from behind, it's because he intends for his opponent to kill him.
- This is a good idea in tabletop RPGs in general, since few players like to hear "oops, looks like you weren't paranoid enough and now your character is dead". Can, however, come back to bite the Game Master if the players ever get it into their heads that the same underhanded tactics this trope bars NPCs from employing should of course be a-ok for their characters...
- The various Warhammer 40,000 RPGs (Dark Heresy, Rogue Trader, Deathwatch, Black Crusade and Only War) seem to regard this rule as entirely optional, given that there are numerous Talents players can take to protect themselves from this (notably, the Light Sleeper talent lets you make Awareness checks as if awake while asleep; there's a whole raft of others devoted to making you better able to deal with being surprised).
- The Elder Scrolls III: Morrowind's Tribunal expansion kicks off when you are attacked by Dark Brotherhood assassins in your sleep. However, for whatever reason, they wake you up before attacking, giving you a chance to fight back. Considering these assassins are supposed to be among the best (and most amoral) killers in the region, their making a noise when attempting to kill you - every single time - seems quite odd.
- Subverted in Call of Cthulhu: Dark Corners of the Earth, where if the player uses the action button on the bed to sleep before bolting all the doors, they don't get to wake up, they merely get a game over.
- A bit of Fridge Logic sets in when you notice that the player character wakes up before getting attacked only if you bolt the doors.
- In Arcanum assassins will not only stand and announce them selfs, but converse with the player before attacking
- Lampshaded after you learn more about the assassins, their history and their "code of conduct".
- Likewise, several people who hang around in the bars may randomly turn out to be assassins - but it will only be determined if you choose to talk to them.
- The 1999 Alien vs. Predator makes the AI-controlled Aliens much noisier than usual, constantly shrieking and hissing as they close in on you. Given how fast they move and how highly damaging their attacks are, them audibly warning you of their presence was about the only way the Marine's campaign could've been playable at all.
- In the second Neverwinter Nights expansion, a reversal of this occurs if you agree to aid a group of formians (intelligent centaur-like ants) in wiping out a drow base. The game will take control of your character and have a cutscene where you just stroll in through the door and call attention to yourself. Not very wise if you're playing a less-than-direct-assault character.
- Fallout 2 is a subversion in that you can involve yourself in the affairs of the bad guys in quite a few ways before the final confrontation, including prank calling them, giving them a chance to build some kind of profile about you. The only person who is assured to care about you in the end is the last boss.
- Subverted in Super Paper Mario. The Dragon teleports in and offs the whole party during an exposition session halfway through the game. It turns out to be a Batman Gambit on his part to help the heroes gather all the Plot Coupons.
- Subverted in Final Fantasy VII when Sephiroth kills Aeris from a sneak-attack, with no warning.
- Played with in Mass Effect 2. In the opening cinematic, the Normandy SR-1 detects the Collector ship, but does so too late. Played straight again with attempts to destroy Shepard's body to prevent the Lazarus project and again when the Reaper IFF beams the SR-2's position, leading to another Collector surprise attack. Played straight in the Arrival DLC - indoctrinated humans subdue Shepard, then keep them alive (but sedated) until the Reapers arrive. Shepard's cyborg body adjusts before the Reapers get there, allowing them to delay the arrival until the third game.
- The second version has appeared in relation—oddly enough—to the Spy from Team Fortress 2. In particular, the Sniper in "Meet the Spy" hears him approaching and moves to retaliate (not that it stops him from being bested and stabbed in the back anyway). Additionally, the decloaking sound was recently made much louder, which means that particularly aware foes can hear him before he strikes and fight back.
- Mooks in Resident Evil 4 will actually say "Behind you, you idiot!" as they are about to attack. Admittedly they say it in Spanish, but still.
- Averted in Sonic the Hedgehog (2006): Mephiles's original plan was to trick Silver into killing Sonic. When that didn't work Mephiles simply teleported behind him and stabbed him through the chest with a giant energy lance.
- For the most part, the Megaman Battle Network series follows this trope until it is subverted in the fifth and sixth games when some of the enemies finally get smarter and begin targeting Lan and Megaman (mostly Megaman) when their guard is down.
- The Sleep spell in Warcraft III puts an enemy to sleep, but attacking it will wake it up. Its main use is to interrupt channeling spells or remove a powerful unit from action for a while.
- In Assassin's Creed: Revelations, enemies finally appear who use the same tactics as Ezio, with one exception. When they appear out of nowhere, they yell something like, "Die, Assassin!" before stabbing him. This, naturally, gives the player a chance to dodge the sneak attack. That, and the Scare Chord just before they strike. Possibly justified by Ezio's supernaturally heightened senses.
- Fire Emblem:
- Very noticeable in Fire Emblem Awakening. Several enemy characters have the ability to teleport - the Valmese sorcerer Excellus and the Grimleal sorcerer Valdar being the two most notable. Alright... well, those two are both important, so maybe they just don't want to expose themselves to the risk of an assassination attempt gone wrong. Fair enough... except we're also treated to a common Risen assassin teleporting in after a mission to try and kill Chrom. None of the villains ever think to try this trick on the numerous occasions that pop up where a hero character needs to be assassinated.
- Justified in Path of Radiance. At one point, King Ashnard and the Black Knight are conspiring to kidnap the heron princess Leanne. Ashnard asks why the Black Knight doesn't just use his Warp Powder to teleport in and grab her. The Knight explains that using the powder drains his strength, so he can't use it in situations that would leave him vulnerable (presumably this also prevents him from using it to launch a sneak attack on the heroes' camp in the middle of the night). But played straight in Radiant Dawn, when the Begnion Senate creates a Rewarp Staff that does the same thing with no drawbacks. They don't seem to realize the advantage this gives them and the most they use it for is to drop by Daein Castle for some Evil Gloating.
- Drowtales: Syphille falls hard into this trope when she attempts to attack Quain'tana, to the point where she could be the page the picture, and it gets her killed. Averted elsewhere in the setting with the Fallen Legion, who excel at this type of combat, and Kalki, who twice now has used this type of attack to kill someone.
- From 8-Bit Theater, two ninjas discuss the merits of shouting "Surprise Attack!"
Ninja 1: Hey, they're dead, aren't they? So what's it matter, hm?
Ninja 2: Well, there used to be six of us, now there isn't.
- Played with in The Order of the Stick. Rogues yell out "Sneak Attack!" whenever they perform a sneak attack. The Thieves Guild berates their fighter for yelling out "Power Attack!" when he uses that feat.
- Nale averts it a few times, stabbing Elan from behind in their first encounter and killing the chief of police without calling his sneak attack in Cliffport. He sarcastically and smugly apologizes for the breach of protocol afterwards.
- Averted to no end in Homestuck. Bec Noir has implemented his teleportation powers for the purpose of killing characters more than once.
- Averted and inverted in DM of the Rings, where Legolas shoots Saruman during parlay.