Pacifist Run

In games that give you a choice between using lethal or non-lethal force in order to overcome enemies, the former method is usually the most convenient. Some gamers like to play through such games while avoiding any killings that are not absolutely required, even if there is no real reward for doing so. Occasionally, a Pacifist Run does provide in-game rewards... or is necessary for 100% Completion.

Compare Stealth Based Games and Stealth-Based Missions.

Action Adventure

 * The Legend of Zelda: A Link to the Past makes this easier than other games in the series because of two factors: The Magic Cape item, and the fact that the game doesn't use the "lock the player in a room and the only way to get out is to kill all the monsters in it" trick as much as other games in the series.

Action Game

 * In an old computer game, Pharoah's Tomb, you only have to kill two monsters in the first part. You do get a reward though: you have a maximum of 5 spears, and getting a 6th gives you a lot of points.
 * Many of the Tomb Raider games have been criticized for not allowing for pacifist runs, as the player is often required to kill wildlife and human characters in order to proceed.

Driving Game

 * Fatal Racing. Surprisingly easy to do unconsciously before you learn how to play the crash/fatality system, surprisingly hard to do consciously after you do.
 * In the classic arcade game Bump n' Jump, where the objective was generally to run as many other cars off the road as you could without crashing yourself, you got substantial bonus points if you completed a level without running anyone off the road.

Fighting Game

 * In Super Smash Bros.., there's actually a bonus ("Switzerland") for clearing a stage without even attempting an attack. Given how many stages have level hazards, this isn't as difficult as it sounds to obtain.
 * In the sequel, Super Smash Bros. Melee, this bonus still exists, although it also requires not being attacked as well (complete neutrality). There is however, another bonus, called, "Pacifist", which does not have this extra requirement. Yet another bonus is called "Peaceful Warrior," which lets you attack an enemy but not KO them. And all of these are necessary for 100% Completion.
 * Easiest way to get Switzerland bonus in Melee: play the Big Blue platformer stage in Adventure Mode without using your third jump.

First-Person Shooter

 * In the Halo trilogy, not counting bosses in 2/3 you can kill 0 enemies and win.
 * In Deus Ex, only two characters have to be fought in order to complete the game; neither have to be killed and both can be circumvented. The first can have an injured NPC open the door they guard, and the second can be knocked unconscious and is also quite willing to blow himself up for you due to poor AI. The rest can be stunned or circumvented in various fashions. The game encourages pacifism in the first level by having characters react positively to you if you don't slaughter everything in sight, but after that there's no longer any explicit encouragement, and it's strictly a matter of pride (although you will get bitched out for slaughtering civilians).
 * the game acts as if you killed the first character even if you circumvent her, due to the game's intent of railroading you into killing. However, given the nature of the game and one could always claim that she was killed by someone else for her failure and/or knowing to much after you escaped and were being framed for the killing.
 * The Nameless Mod lets you avoid all enemies, including bosses. With some endings, you can finish the game as an Actual Pacifist.
 * 2027 also allows this, however, you will not be able to complete the final
 * Invisible War picks this up, as even plot-critical deaths are optional. The benefits manifest differently depending on which faction wants them dead and how their death affects gameplay (keeping one person alive grants access to a weapon you won't seriously need till the end), but ultimately there are no required kills. A hidden bonus is that the wrap party has a lot more patrons the less people you kill.
 * Deus Ex Human Revolution, like the original, has only a handful of forced boss battles where you are required to kill. There is an achievement for doing a pacifist run (excepting the boss battles). Storyline wise, it makes sense, because the bosses are absolutely insane and have very much crossed the Moral Event Horizon.
 * The game is also notable for there being scenarios that have made players willingly abandon their Pacifist Runs. It's kind of hard to keep using limited force when witnessing atrocities like  or  . Some players reported that   led to a complete murder spree against them.
 * In Team Fortress 2, the Medic class achievement "First Do No Harm" entails reaching the top of the scoreboard in a game of six or more players on a team without killing anyone, instead relying on assist kills while healing others. Given the likelihood of spies looking to tear you a medically redundant new behind, it's just as tough as it sounds.
 * However, you can cheat by playing most of the round as another class, getting a high enough scoreboard position, switching to Medic, and then getting a single point without hurting anyone directly.
 * Then again, if you have a good team that covers for the medic it's not really that difficult, although on most random pub servers you won't have such a team.
 * Ideally, the Medic wants to help at least two players have incredibly good games. If he helps only one player, they will naturally top the team because Kills are worth more than Assists. So to get this achievement, the more people you help get kills(and thus the more assists you get without making your own rival), the better. If you help three teammates get 20 kills each, they have 20 kills and you have 30 points from 60 assists!
 * The Scout has a similar achievement called "No Hitter", where you capture the intel and bring is back without firing a shot (the icon is even a dove holding an olive branch above an intel case). Not nearly as hard to do, as a lot of people with the intel forgo attacking to just flat-out run anyway.
 * Under the rules of the Doom speedrunning site Compet-n (adopted by other sites like the Doomed Speed Demos Archive,) one of the demo categories is "UV pacifist," where the player must complete a level on the "Ultra-Violence" (Hard) difficulty setting without harming any monsters. (Monster infighting and unintentional telefrags are allowed.)
 * Painkiller has this as one of the card conditions in Battle Out of Hell...sort of: The card condition for the Loony Park level is to finish with no more than 88 kills, meaning that the last section of the level has to be finished with minimal casualties. Fortunately, it's a rail shooter section to boot, so if the player has enough health, there's nothing stopping him from going and fetching another cup of coffee while the rail section plays out.
 * In Perfect Dark, the player has the ability to disarm opponents. Most enemies who get disarmed will give up, but some may pull out another gun, pick up the dropped weapon, or attempt to punch the player, in which case you can simply knock them unconscious with a punch or pistol whip.
 * Despite its reputation for spectacular violence, Soldier of Fortune allows the player to pull this trope off by blowing weapons out of the enemies' hands, rendering them non-threatening.
 * Two of Metro 2033's achievements are awarded for relying on stealth instead of violence: Cross "Frontline" without killing any soldiers (of either faction) to get "Invisible Man", and infiltrate "Black Station" without killing any guards to get "Merciful." Notably, there's another achievement for doing the exact oppposite in "Frontline," so you'll have to master both styles of play if you're going for One Hundred Percent Completion. Avoiding killing human opponents also gives you hidden points, which counts towards the hidden/good ending.

MMORPGs

 * In Dungeons and Dragons Online, an experience bonus is awarded to the players if they can complete a quest with zero or otherwise minimal kills.
 * There is one player in World of Warcraft who is actually attempting to level to 70 without killing anything.
 * This also inspires a debate as to whether a player limiting themselves to "only" healing allies really counts; if the allies kill enemies you still get the rewards.
 * With the release of Cataclysm, pacifist levelling became much easier due to Herbalism and Mining now granting experience for picking plants and mining ores. This can lead to the rather amusing result of some random schmoe who picked a lot of herbs becoming more powerful than an Old God.
 * Archaeology can also give surprisingly large amount of experience.
 * On the notable pre-MMORPG text MMORPG Gem Stone (now in its fourth iteration, as Gem Stone IV), it was extremely easy to get from level 0 to level 1 simply by visiting certain areas in the main town you started in, which gave you 1000-1500 experience of the 10,000 you needed simply by seeing them for the first time, as well as taking an interactive newbie tutorial which garnered you several thousand experience. However, after that, there were a couple of ways to gain experience without ever actually harming anyone. Anyone with sufficient lockpicking skill could gain experience by opening boxes that players found on dead enemies. One class, called empaths, could actually heal other people of their physical damage by transferring it to themselves, which also garnered experience points. Finally, if you really wanted, throwing trash away in trashcans gained you 1 point per item. So theoretically, you could throw away 10,000 things and level up.
 * Discworld MUD has many ways of advancing character without killing, including exploration, quests and using skills. This way is generally slower, but also requires less effort. There is even a special therm for it, quoting official wiki, "Idlechasing, the art of getting as much experience as possible by using commands, usually without going on a killing rampage or moving much".

Platform Game

 * In the original Prince of Persia, it was possible to get past the guards by careful use of parrying and moving forward. Of course, this meant they were still there if you had to go back the way you came... You still had to slay Jaffar, though he came back in the sequel.
 * Beating Mega Man 9 by only attacking bosses and mid-bosses is actually a bonus needed for 100% Completion.
 * Some of the challenges in Contra 4 are pacifism challenges, which strip you of all weapons.
 * The First Person Le Parkour game Mirror's Edge gives you an unlockable achievement, "Test of Faith", if you finish the game without killing anyone with a firearm. Funnily enough, the achievement is only for not shooting anyone... you can throw as many cops off 100-story buildings as you like and still be considered Le Buddha.
 * It's actually one of the selling points of the game that you can finish the entire thing without firing a gun at anyone, which is pretty much unique among first-person-perspective games (discounting medieval and fantasy games and the Myst series and its clones).
 * Doesn't stop you punching/kicking the snot out of the opposition, though it's not like you stop to break their necks, so they probably are really just unconscious. Apart from the poor guys that get kicked/thrown/punched off buildings. Besides, those blasted deserve it, they're like ninjas, but without the inverse law!
 * For even more of a challenge, try to get the Test of Faith achievement/trophy on the hardest difficulty setting. It's very satisfying.
 * The title character of adventure/platform shooter Iji wakes up to find that aliens have invaded and scientists have implanted her with nanotechnology to combat them. Being a teenage girl, Iji is uneasy with the idea of killing, even though the aliens have killed most of her family. The game is designed to give you a choice - you can go in guns blazing and kill hundreds as in so many other games, or you can deliberately avoid bloodshed. The ending is the same whether you kill one or fifty enemies, but there are some Easter Eggs as a reward for completely holding your fire.
 * Doing a pacifist run sometimes adds new challenges to a stage. The third stage, for example, has a requirement of not coming into contact with any Tasen soldiers. Otherwise, you won't be able to skip, and will be forced to kill them.
 * From version 1.3 onwards, it is possible to have a perfect zero number of kills in all but the hardest difficulty due to not being able to skip a boss.
 * Version 1.6 also allows a "technically" pacifist game that can still have a high death toll, as reflecting enemy projectiles back at them no longer counts as a kill. Also, the player can deliberately get hit by rockets so that nearby enemies get killed by friendly fire.
 * Trine has a Steam PS 3 Trophy where you have to complete a level without killing a single enemy.
 * This is the point of the missions involving the Spirit of Kindness in Yoshi Topsy-Turvy. The less enemies you kill, the better Happiness Medal you get.
 * Brawl in the Family's Ode to Minions inspired at least one person with a Youtube account to play Super Mario World without killing anything. And really, it would inspire anyone to. Just listen to it.
 * Someone did this for Commander Keen 4 on hard mode without saving in level. Since the game was designed assuming the player saved constantly, it quickly becomes very difficult. It can be found here.

Roguelike

 * In Nethack, 'pacifism' is one of the many voluntary conduct challenges that is tracked by the game (along with atheism, vegetarianism, breatharianism, illiteracy, etc). Put in scare-quotes since in Nethack 'pacifism' means that your pets do all the killing instead of you; you can attack the monsters all you want as long as it's not you that lands the killing blow. (You can also wear a ring of conflict to make the monsters kill each other, though then you have to make sure your (usually very powerful) pets don't kill you.) There actually isn't a single creature in the game who must die (as you can steal any important items instead - this applies to Quest Nemesis, Vlad, Rodney, and the High priest), but winning without you or your pets killing anything is pretty much impossible.
 * There's also the 'never hit with a wielded weapon' conduct, which holds a bit closer to the spirit of the thing (though barehanded martial arts and magic are still permitted). It can also be combined with the above for extra masochism.
 * If you want to complete your Baroque collection in Baroque, you'll have to do at least one run through the Neuro Tower without killing purifying any Meta-Beings. This is made a bit tricky by the fact that certain Meta-Beings like to block your path, forcing you to hit them until they get out of your way.

Role-Playing Game

 * The Fallout series is notable for the possibility of not needing to kill anyone, although you will be indirectly responsible for the deaths of quite a few people (and, in some cases, populations). In most of the series it is even possible (although very hard) to do an evil pacifist run.
 * Fallout 3 is, however, impossible to complete without directly killing anything. It starts with the requirement to kill a radroach to complete the second tutorial, and moves on from there.
 * And even if your pacificism only applies to humans, and possibly ghouls and mutants, it's impossible to complete New Vegas without murdering at least one person. Three of the four endings require killing Mr. House, and in the ending where you work for Mr. House, you have to
 * You technically don't have to kill Mr. House, but simply disable him from the system of the Lucky 38. He eventually will die from it anyway, since he is now removed from his sealed capsule, but the player does not directly kill him, making it (kind of) possible to avoid killing anybody.
 * doesn't need to involve killing anybody. You certainly can go in, guns blazing, and slaughter the whole lot of them (though this isn't recommended as  is almost entirely composed of high level Elite Mooks), but there is an alternate route in which their base's reactor can be made to self-destruct. Taking this route has the base computer tell the populace to evacuate in an orderly manner. Nevertheless, their faction is effectively destroyed due to their resources being annihilated, even if their personnel are just fine.
 * Due to the nature of the game, a Pacifist Run is wholly impossible in Fallout Tactics.
 * Feros in Mass Effect has a mission where you can choose to simply knock out the colonists being controlled by the local Eldritch Abomination instead of killing them. While this makes the mission much more difficult it is definitely worth it for a Paragon Shepard.
 * One player managed to do this in Might and Magic 7 as shown here.
 * In Planescape: Torment, you can get through the whole game having to fight only four (Don't forget the zombie at the beginning who has the key out of the starting room!) characters, and you don't necessarily have to kill any of them. You're forced to "kill" the first character you have to fight this way, but it's just a Non-Lethal KO. Then again, this should come as little surprise in a game where a major objective is to find out why you can't die.
 * Ultima IV encourages this somewhat, you still have to fight monsters to get Valor points, but letting them run away instead of killing them gives you Compassion points.
 * Additionally, killing enemies that aren't evil (hungry or defensive animals and the like) will decrease your virtue points.
 * In Ultima VI, it's quite possible to complete the main quest without killing anybody. There are only few monster occupied areas that you must visit to advance the plot and it's possible to avoid combat in those by using invisibility rings and potions to slip by enemies unnoticed.
 * In Ultima VII, you only have to kill  at the end.
 * In the Bakumatsu chapter of Live a Live, Oboro keeps a running mental tally of how many people he's killed (only humans; ghosts, demons, and machines don't count towards this total) over the course of the chapter. Somewhat overlapping with the Stealth Run, finishing the chapter with zero kills (which requires a good number of counterintuitive steps) nets you his Infinity Plus 0.5 Sword for use in the final chapter. Of course, it's possible to get an equivalent weapon by beating a rather difficult Bonus Boss.
 * A common and useful Game Breaker in Final Fantasy VIII is simply to junction 100 Break spells to your weapon's elemental attack and hit enemies with that when you otherwise just can't run away. Doing this keeps you from gaining experience and levels, which helps in the long run once you find decent spells to junction to your physical stats.
 * It's possible to get to the final boss of King's Field II while only killing one monster: a red mushroom that you can't get past on a narrow path. You're still level 1.
 * In Alpha Protocol, it is possible to get through the entire game without ever using lethal force on any opponent, outside of a couple of armored vehicles and one cutscene-mandated kill (dropping al-Shaheed's bodyguard off the bridge). In fact, this method is quite viable, if Mike has specializations in pistols, stealth, martial arts, and toughness. Make use of tranquilizer darts, stealth with nonlethal takedowns, unarmed attacks, and nonlethal gadgets like shock traps and flashbangs, and Mike can potentially get through the whole game with no kills. The game even keeps track of this (with the "Orphans Created" stat) and rewards the player with perks that boost the effectiveness of his stealth and other nonlethal skills.
 * It's not exactly a Pacifist Run, but Geneforge 4 occasionally mentions that a "great Shaper" can get through the game without ever lifting a hand in defense. This variously means sneaking past baddies, abusing the Leadership skill, and luring enemies to weapon-toting allies.

Shoot'Em Up

 * In Star Wars Trilogy Arcade, during the sequence on Endor on the speederbikes, you gain bonus points (called Bloodless) for shooting down the enemy's speederbikes instead of the enemy themselves. But considering they're speeding pretty fast in a forest full of trees, it probably would have been less painful to have been instantly shot to death.
 * The original Star Wars the Arcade Game Vector Game gave a bonus if you 'used the force' and took no shots in the Death Star Trench except the single torpedo shot into the exhaust port, instead dodging the massive incoming fire.
 * Ikaruga, by virtue of inheriting twenty years of evolution in the shooter genre, allows the player to complete the game without ever firing a single shot. Your reward is the rank of Dot Eater.
 * Star FOX 64 offered an interesting variant since bosses are worth more "kills" if they are defeated fast, so players attempting this had to wait a while in those fights while dodging the attacks and (depending on the exact definition and route) protecting their teammates in those cases where they can actually get attacked by these bosses.
 * R-Type Delta and Final both feature bosses which are automatically destroyed after a certain time; late in the game, bosses will instead kill you if the time limit expires, so the Pacifist Run is to destroy only these bosses. Can be made even harder if combined with a no-Force run, which severely decreases the defensive abilities of the player's ship.
 * All Gradius bosses—including the final bosses—self-destruct after a certain time, as well. Of course most of them don't fight back anyway.
 * As in other vertical shooters, this is a common type of run in the Touhou series despite the fact that the games actively punish trying to do this. Most Final Bosses and Bonus Bosses have their final spellcard become incredibly difficult if you take too long, but have long enough timers that the average player will never see this. And there'll generally be a few patterns that will just get worse with time, and the occasional wave of enemies that will exit through the bottom of the screen, where the player is, if not killed.
 * Geometry Wars: Retro Evolved has an Achievement called Pacifist. To get it, you must not fire for the first 60 seconds of the game. Since the fast, homing square enemies spawn before that, it's a Nintendo Hard one to get.
 * The sequel has a separate game mode called Pacifism, where the objective is to avoid the said square enemies as long as possible. While you may not fire, going through a gate causes a shockwave that kills nearby enemies. In addition, the King mode has an achievement called Treaty and the Wave mode has an achievement called Surf.
 * Afterburner Climax with only 1 kill, possibly avoidable? Why the hell not?
 * The Taito arcade game Night Striker has a bonus called the Pacifist Bonus, where if you do not shoot at anything, you earn 2,000,000 points. This bonus stacks up per stage for six stages. (ST.1 - 2 mil, ST.2 - 4 mil, ST.3 - 6 mil, etc.) An example of this in action can be seen here
 * Then there's a playerdoing a complete pacifist only run.
 * NARC allowed you to "bust" (handcuff) enemies instead of killing them. Doing so was worth MANY more points than killing them, making it easier to gain bonus lives (necessary!). Only about half of the enemies could be "busted" though.

Simulation Game

 * This is half of what it's like to try and be a benevolent god in Black and White. The other half is being nice to your villagers.

Stealth Based Game

 * Aside from the bosses, it is possible to get through most Metal Gear Solid games without ever killing someone. (The first one is an exception—you are forced to fight off a horde of guards at one point without access to nonlethal weaponry.) In the original, this just earned the player a suitably passive animal code name after the end credits. In the later games, you are given rewards for keeping enemy fatalities to a minimum.
 * This became considerably easier with the Tranquilizer weapons in later games, resulting in an even more difficult variation—No Tranquilizer Run.
 * In Metal Gear Solid 2, since only two of the bosses are actually story-killed by you, no real difference is made whether you stamina-kill them or not (only that a stamina-kill doesn't show up on your score as a real kill). Interestingly, not-killing Fatman, one of the story-killed bosses, results in him passing out at the end of his dying speech instead of dying. When Ocelot remarks on Fatman's death later on, the line is the same, but the implication is that Ocelot killed him rather than you, which provides a neat clue as to Ocelot's real alignment...
 * In Metal Gear Solid 3, you can even not kill the bosses—sort of. They have non-lethal hit bars, and you get a special bonus for defeating a boss with non-lethal force... but if they were supposed to die, they commit suicide in the following cutscene. However, there is one exception:
 * In the case of the Cobra Unit, specifically, their "microbomb" blows up, and they say their codename. In that order.
 * The Fear is one boss that actually becomes easier to stamina kill. He jumps around and constantly loses stamina, plus you can land a few shots of him. But he can also replenish it, by hunting food that he eats. But he will eat any food you have. And just place some rotten food close to him...
 * To be fair, The End is so ridiculously old and infirm that pumping him full of tranquilizers would likely be just as lethal as filling him with bullets...
 * Metal Gear Solid 4 also allows you to take out all of the bosses using non-lethal means. Unlike the other games though, it actually affects the cutscene afterward. The difference is really subtle leading to many players thinking Kojima was lying when he said you could save them.
 * Even MGS4's online mode gets in on this, giving players the "Pigeon" ranking if they have a suitable ratio of kills to knockouts.
 * Metal Gear Solid 4: Guns of the Patriots is the first game in the series to let you do a true no-kills run, not even story kills. Although you can (and once, you must) blow up as many Gekko and Dwarf Gekko as you like.
 * Metal Gear Solid Peace Walker lets you do a pacifist run one step at a time. Each of its stages are mission-based, letting you do a perfect no-kills stealth run once you're properly prepared, even against a missile tank supported by thirty troops.
 * Metal Gear Solid Rising has confirmed it will have a Pacifist Run, and will award an Achievement for it.
 * Not anymore, it won't. Metal Gear Rising: Revengeance is making a complete shift to the Hack and Slash genre, so this aspect's surely going to get dumped.
 * In Splinter Cell, it is possible to complete the game with only one overt kill, which is a required mission objective. This is usually accomplished with liberal use of the "sticky camera" pseudoweapon to knock enemies out.
 * Three mandatory assassination mission objectives aside, in Splinter Cell: Chaos Theory it is possible to complete the game without killing any enemies. Mission requirements aside (e.g. knocking out a guard so a helicopter will come) it is possible to complete the game without knocking out more than three enemies (Bathhouse boiler room), and perhaps fewer.
 * Most missions in the various Hitman games can be completed without killing anyone other than the mission's intended target(s). In Hitman 2 and onward, doing so earns the player the rating "Silent Assassin" and usually comes with a reward of some sort.
 * In the fourth game, Blood Money, killing anyone other than the target(s) can make later missions more difficult as your notoriety will grow, especially if you leave witnesses and/or get caught on camera. However, you can obtain the surveillance tape if you get caught on camera before leaving the mission, and pay money to cover up the crime after the mission. Killing witnesses, however, can make things worse.
 * It should also be noted that, technically, a zero kill run of much of Blood Money is possible, owing to the fact that "accidents" are counted separately from outright kills and (unless you kill a VIP) have no impact on your rating (even if you kill civilians).
 * And then the entire thing gets turned on its head in the final mission.
 * The Thief games, on higher difficulties, sometimes require you not kill anyone in a mission. Ideally, you do so by just getting around without being noticed. If you must pop someone, though, you have a blackjack which can knock the unaware out in a single strike. Note that you can play through the entire first game and second game without knocking out anyone or anything, let alone killing them.
 * Doesn't apply to the second game, as
 * The third and final game can also be completed without a single kill or knockout, which includes plot-kills since the Big Bad can't be killed anyway and isn't explicitly killed at the end either.
 * Oddworld: Stranger's Wrath, being a Bounty Hunter themed game, allows you to choose between killing an enemy, or simply stunning them long enough for you to trap then in your bounty bag. Live enemies are worth more than dead enemies. Challenges could include bringing in all bounties alive, bringing in all outlaws alive, or bringing in all enemies in the game alive. Minor challenges could also include never attacking a non hostile NPC for Moolah, or neglecting to collect two optional Moolah rewards that require robbing innocents.
 * In Tenchu: The Shadow Assassin the player gets the highest rank S, Phantom, for finishing a level without killing and without being seen.
 * And in Wrath of Heaven there is one level in which, at first, you can't kill any guard.

Survival Horror

 * The remake of Resident Evil for the Game Cube has what is called "One Dangerous Zombie" mode, wherein a zombie completely strapped with explosives constantly follows you around through the game. Attack him even passively, and you get a game over. For the series proper, you obviously need to kill bosses in the main plotlines, but for standard Mooks and some of the minigames, you're totally free to try this challenge out.
 * The bitch is that "One Dangerous Zombie" isn't a selectable mode; it's automatically foisted on you during a New Game+ whether you like it or not. The good news, as it were, is that said zombie disappears once you leave the mansion and go to the guardhouse.

Third-Person Shooter

 * Playing Postal 2 without ever killing anyone gives you the end-of-game rank "Thank you for playing, JESUS!"
 * The same holds true of the expansion pack, Apocalypse Weekend, but it's all theoretical since it's impossible to actually beat the game without killing anyone. It's more linear and combat-oriented than the original Postal 2, and there are several characters you have to kill to proceed. Hell, even the zombies count as kills, and there are at least 2 different missions where you have to destroy a certain number of them to proceed forward.
 * Second Sight tracks your "morality" score for each level of the game, which starts at 100% and decreases with each enemy you kill. Players can avoid killing enemies by tranquilizing them, sneaking past, luring them into hazardous terrain features, allowing NPC allies to kill them, or tricking them into killing each other. It appears that only four enemies, (Not counting your involuntary initial manifestations of Psy-Attack, and improved telekinesis) actually have to be killed. . Oddly, even without killing anyone else the big bad will still call you out for all the bodies you stepped over to reach him.
 * He means stepped over. The game also keeps track of how many km of "muddy feet" you walked per level i.e.: how far you walked with your shoes covered in blood from enemies you killed. Yeuuchh...
 * In Prototype, it is literally impossible to go through the game without killing civilians. The closest the player can get to a self-imposed pacifist challenge is to try to keep their civilian kill count as low as possible (difficult, since you can kill them by running into them). There is an achievement for eating only 10 or less civilians.
 * In Reservoir Dogs there's a choice to go either "Psycho" or "Professional", the latter being if you concentrate on using hostages over shooting people. The issue is that hostages loss HP over time... due to stress?

Turn-Based Strategy

 * Fire Emblem doesn't normally lend itself to Pacifist Runs, since you need kills to level up. However, Thracia 776 allows you to non-lethally KO enemies and hold capture them - in fact, you can steal their equipment and use it for yourself when you do! The only limitation is that, in order to capture a foe, the enemy's Build stat must be lower than that of the unit doing the capturing (Then again, Fin, who has 20 Build, is available from the start of the game), and when you use the capture command, the capturing unit will have his stats reduced for the turn.
 * In Jagged Alliance 2 you can finish the game without killing anyone except the queen and without liberating any towns just by cutting across country to the capital, sneaking past the soldiers there, and killing the queen before any of her guards arrive.
 * Galactic Civilizations: you don't get an achievement for it, but you can win by forming Alliances with all the other races, forming an Alliance with one race and having them crush your enemies, or by using heavily upgraded influence starbases to either culture-hug enemy worlds into defecting to your side, or to mark most of the map as your territory (which brings with it the incidental bonus that you can ram through any result you want at the United Planets and nobody will have the voting power to stop you).

Wide Open Sandbox

 * Red Dead Redemption. You can minimize all killing in the game with your trusty lasso - aside from times you must kill, such as the gatling gun missions - but it's Nintendo Hard to do the entire game that way.
 * It's possible to play through all the X-Universe games without killing anyone directly, or without killing anyone at all (provided you don't do the plots). The goal is to keep your combat rank at "Harmless", which means you have zero kills. If you kill any enemy, the rank goes up and takes several real-time hours to go back down.