'Duke Nukem 3D' has a hanged monk in Deathrow as a reference to Rise of the Triad as well as a literal hung jury in Pigsty.
In Final Fantasy VI, after spending a year in a coma after The End of the World as We Know It, if you fail to save Cid, Celes, having lost everything, decides to climbs a cliff to leap off onto the rocks below (which, according to Cid, all other survivors in the island had done when they succumbed to despair). She survives on a miracle, sees Locke's bandanna wrapped around a pigeon's wing, and regains her will to live.
Shadow does this in his segment of the game's ending if you have him in your party. To sum up his motivations, he'd let a friend die a very painful death instead of finishing him himself and has carried the guilt for years with him. With the world saved, he stays in the collapsing final dungeon to die and join his friend in death. Complete with him telling his dog to go on without him. Tear Jerker, ahoy.
In Final Fantasy VII, When Barret confronts his old friend Dyne, they duke it out. After defeat brings him back to his senses, Dyne realizes the horrible things he's done and tells Barret to keep taking care of Marlene, who was his child by birth, saying his hands are too stained to carry her anymore. Then he drags himself to a cliff and throws himself off it. The game conveniently forgets that he actually survived that same drop years before.
God of War starts with Kratos throwing himself off a cliff, with the game being a How We Got Here. The Gods decide that You Kill It, You Bought It and therefore promote him as the new God of War. This turns out badly for them when they renege on this decision.
In the Phoenix Wright: Ace Attorney universe, quite a few people in backstories. Redd White in particular is apparently responsible for a large number of instances of this (as the driver, not the drivee).
Notably subverted in Justice For All. "Prosecutor Miles Edgeworth Chooses Death." No, he didn't.
And played straight in the same case, regarding Adrian Andrews' former mentor Celeste Inpax, who hung herself two years ago after being dumped by Juan Corrida, after he had learned that she was ALSO dumped by his rival Matt Engarde and refused to "accept his leftovers".
In addition to that, Adrian Andrews attempted to kill herself less than a week later, unable to bear living without Celeste. She failed.
Terry Fawles does it onscreen in the courtroom in Trials and Tribulations. His girlfriend Dahlia really messed him up.
Speaking of Dahlia, in 3-5, she taunts Phoenix by drawing the conclusion that Maya accidentally killed her mother, then killed herself out of sheer guilt. Fortunately, she's proven wrong on both accounts a bit later.
Also happens in the fourth game: not in any of Apollo's cases, but in the flashback segment of 4-4, the supposed murder victim, Magnifi Grammarye, committed suicide.
In The World Ends with You, Joshua, supposedly.He's likely to be lying, but if it was suicide it didn't occur recently.
It's implied somewhat that Shiki committed suicide too.
In the Visual NovelHeart de Roommate, the gang attempt to befriend a rather lonely schoolgirl with a past history of attempted suicide. This leads to one of the darkest scenes in the game, when during a conversation with the main character on the roof she accuses him of only being interested because he fancies her and offers to have sex with him if he'll leave her alone. When he refuses she proceeds to make another offer... sleep with her or she'll scream that he's a rapist and jump off the roof, something that seems quite plausible given her past history and self destructive personality. She doesn't go through with it no matter what the player chooses, though accepting her offer leads to a rather bleak Nonstandard Game Over.
Drakengard has two examples. The first one is Leonard, who comes home to see his family dead and his home razed by the evil Empire. Feeling that he has failed to protect them, he gets very close to cutting his own throat, only being stopped by a malicious fairy. The second is the protagonist's sister, who, due to Mind Rape and her brother being disgusted by her incestuous feelings for him, commits suicide to escape disgrace.
One of the bad endings in School Days has this too: Kotonoha Katsura, the Ojou of the story, throws herself off a building if Makoto (in the main player's shoes) goes with Sekai instead. And she actually dies in front of Sekai and Makoto (High-Pressure Blood and all), traumatising them so badly that Makoto not only breaks up with Sekai, but swears off romanceforever.
In System Shock 2, Dr. Janice Polito was driven to suicide when she found out that she unleashed SHODAN. You find her corpse in her office, and her suicide note in the Rickenbacker church.
A "ghost" crew member snaps under the horror of what's happening, says sorry to his wife and children, and shoots himself. Several corpses are found sitting with a gun in their hands, implying they've chosen the same way out.
In the end of Super Robot Wars Original Generation 2 (and Advance too), being the 'only survivor' of the Shadow Mirror, Lamia Loveless thought that she has failed her mission, killed her teammates and superiors, and is a defective product all around, and thus she attempts to self destruct... only to be stopped by her new teammates just in time and be persuaded to live her life in the current world. She actually has more self-destruct attempts throughout the series, but only this occasion fits the trope.
Starcraft: Gerard DuGalle commits suicide after his defeat, in remorse over his gullibility and murder of Alexei Stukov.
Super Fire Pro Wrestling Special featured a story where, about halfway through, things get worse, and worse, and worse... First, you suffer a string of defeats. Then, your coach winds up dead. Then, you accidentally kill your opponent in one match. Then, your girlfriend leaves you. Then, your opponent for the championship, a Ric FlairExpy, kills your tag-team partner AND reveals that he was the one who killed your coach. Once you defeat the murderer and take the championship for your own, though, the hero realizes that it really is lonely at the top. He shoots himself in the head three days later. Would it be any surprise that this particular game's story was written by a rookie Suda51?
Yume Nikki: After dropping the 24 effects off in the Nexus, Madotsuki wakes up from her dream, walks out onto the balcony... and leaps off the edge. Cut to black and a bloody red smear on the canvas.
In Illusion of Gaia - Will is forced into a game of Russian Roulette using a poisoned drink. Will's psychic powers allow him him to dodge the poison, but the other player, Straw Hat, drinks the poisoned shot anyway, out of sheer wounded pride. After this, you read a letter from him telling you he had a terminal disease and was playing the Russian Glass Game so that his pregnant wife would be finacially secure after his death. He had nothing to lose by drinking the poison.
Rivet City has Mister Lopez, a suicidal senior whose family was killed by Raiders, standing at the top of the Bridge Tower. You can either convince him to jump to his death (bad Karma), or talk him out of it (good Karma).
In Fallout: New Vegas, if you tell Ranger Chief Hanlon that you know he's the one behind the bizarre intelligence reports to get the Rangers out of what he considers a Hopeless War, he'll excuse himself, announce his misdeeds to Camp Golf, and shoot himself in the head.
Captain Curtis, a Legion mole in Camp McCarran, also kills himself after you report him to Colonel Hsu, providing you didn't kill him yourself.
Also in Fallout: New Vegas, when the security came on-line at the Sierra Madre Casino, some of the guests killed themselves to avoid dying of starvation or being killed by security. This was the ultimate fate of Vera Keyes, the singer for whom the casino was built.
If General Oliver was talked down in the House ending, Mr. House will state that Oliver has a roughly 40% chance of committing suicide since he'll be publicly disgraced and held responsible for losing the war once he returns to NCR territory, with his hopes of pursuing a political career dashed to the ground. The same probably applies in the Independent Vegas ending.
Near the end of Dead Money, you have to stop Dog from blowing himself up and taking the whole casino with him, by turning off the gas valves in the kitchen without being spotted. After that, you can have him die a less overkill death via self-inflicted Neck Snap, or talk him out of it.
In Boone's Vengeful NCR ending, he takes his own life after sniping the ranger who ordered the attack on Bitter Springs. In the Vengeful Legion ending, he stages a suicidal charge against the Legion, leading to him being crucified.
In Metal Gear Solid 2, it is revealed that Otacon's father drowned himself after finding out that his wife (Otacon's step-mother) and son were having an affair. In the same game, Fortune's mother committed suicide after her husband's death and her son-in-law's imprisonment.
In Metal Gear Solid 3, it's implied that the reason why the Cobra Unit was still utilizing their microbombs essentially delt with this trope. Similarly, it is also argued that Colonel Volgin being hit by lightning was actually intended on his part, due to the way he was reacting just before he was hit by it.
In Metal Gear Solid 4, Vamp and Naomi go out this way after disabling the nanomachines keeping them alive.
In Obs Cure 2, one of the playable characters commits suicide after his girlfriend, and most of his friends have been killed in the 'incidient' at the school. (By incident we mean the surivial horror plot.) The sequel is Darker and Edgier than the orginal, which is no small feat seeing as in the first game everyone dies in horible experiments, or a the hands of the horrible experiments, except for the playable characters.
One popular backstory of the Touhou character Yuyuko Saigyouji is her committing suicide after learning about her power evolving from controlling dead spirits into invoking the death of anything. Fortunately(?) Yukari ensured her spirit could never "cross over" completely, allowing her to continue existing as a Cute Ghost Girl.
Many popular Yuyuko/Yukari fan works have the two be friends, or even a couple, back when Yuyuko was still human. This delves far past Tear Jerker and into soul-crushing territory when you realize Yuyuko doesn't seem to remember anything about her past life, or Yukari. Indeed, some of Yukari's personality characteristics, such as constant sleeping and over-friendliness, are symptoms of depression.
Tai Kaliso in Gears of War 2, after enduring an impossibly brutal series of tortures at the hands of the Locust Horde, puts a shotgun to his chin the moment it is offered to him.
Mass Effect: not only does Fai Dan shoot himself to escape the Thorian's mind control, but other characters can also be Driven to Suicide depending on the player's decisions, including Saren.
Also a Salarian researcher, who shot himself to escape being ripped apart by the rachni.
Ronald Taylor can be left a pistol with which to kill himself.
In Mass Effect 3, both Tali and Samara can potentially commit suicide. The former if the geth destroy the entire Migrant Fleet, and the latter because she's forced to make a choice between obeying the Justicar Code or killing her daughter.
Like Saren before him, The Illusive Man can also be convinced to kill himself to escape Reaper indoctrination in the Grand Finale.
The third game loves this trope. The characters listed here? That's not even half the number that this can happen to. For understandable reasons.
Clone!Shepard does this in the Paragon Ending of the Citadel DLC, refusing to take Shepard's hand and letting themselves fall from the edge of the Normandy ramp. It's implied that their Despair Event Horizon cames after Shepard's friends rushed to save them from falling, while s/he was callously left to die by Brooks, thus answering their earlier rant "What makes you so damn special?" Shepard has friends.
If the Warden sides with Caridin in the "Paragon of Her Kind" quest in Dragon Age: Origins, he gives the Warden a crown before jumping to his death from a high ledge, into a river of lava, to atone for making golemsfrom living dwarves. Zathrian can also be persuaded to end his life—which ends the curse on the werewolves, and frees the Lady of the Forest—in "Nature of the Beast"; it's considered the best ending, being a third option between killing all the werewolves and killing all the elves.
Anders very clearly has a death wish by the end of Dragon Age II, and it is both creepy and heartbreaking.
Setsumi from Narcissu. Probably justified that since she had terminal disease, she's going to die anyway, and she doesn't want to die at home or in the hospital.
Archer, AKA Emiya Shirou of Fate/stay night, except as a spirit existing primarily outside of time he's actually incapable of death, so his suicide plan is killing Shirou so that he can't make the contract with the world and become Archer, hopefully canceling himself out of existence. Several characters point out, including himself, that this is very unlikely to work.
In Dead Space several members of the USG Ishimura crew who already haven't been turned into Necromorphs commit suicide; examples include the man who headbutts a bulkhead until his head is pulped, the woman in the medical bay who severs her throat with a surgical saw, and a woman in Doctor Challus Mercer's evil Unitology Room Full of Crazy who blasts her own head off. Also Isaac's girlfriend Nicole killed herself via lethal injection before the game began; Isaac just doesn't realize it until the end.
And in the sequel, the Unitology cathedral contains groups of dead bodies with plastic bags over their heads and an empty chalice nearby. It's implied that they committed mass suicide so they could be reborn as Necromorphs.
This can also happen to Isaac himself near the end of the second game, if you let Nicole grab him. And, like every other death scene, it's...not pretty, to say the least. He puts himself out with the javelin gun. TO THE HEAD.
Many, many examples can be found in The Suffering. At the beginning of the game, for example, several inmates in Cell Block T hang themselves following the earthquake.
In a vision of the past, a military commander shoots himself rather than face a court-martial.
Another flashback reveals that in 1681, three little girls hurled themselves off a cliff after realising that their seemingly harmless prank had resulted in the execution of eleven innocent people. Unfortunately, they don't stay dead.
Hermes Haight, the prison's most infamous executioner, killed himself in the gas chamber; according to his poisonous ghost, this was the final step in a very long obsession with learning what his victims felt.
A heroin addict blows his brains out with a shotgun, apparently unable to "weather the low."
Three inmates in solitary confinement at East Baltimore Correctional committed suicide rather than spend another six months alone in the darkness.
It's revealed that inmate Ranse Truman tried to slit his wrists with a sharpened spoon after spending a few months on Carnate Island and exploring its unique history. When you meet him in the second game, he appears to have tried to cut his throat at some point.
In Robot Alchemic Drive, Nanao kills herself if the building where she works is crushed too many times.
HK-47: Statement: Oh, yes. My master had quite the collection of tortured individuals that seemed unable to confront their basic personality conflicts. Let me cite some specific examples. Mockery: [mimicking Carth's voice] "Oh, master, I do not trust you! I cannot trust you or anyone ever again!" Mockery: [mimicking Bastila's voice] "Oh, master, I love you but I hate all you stand for, but I think we should go press our slimy, mucus-covered lips together in the cargo hold!" Conclusion: Such pheromone-driven responses never cease to decrease the charge in my capacitors and make me wish I could put a blaster pistol to my behavior core and pull the trigger.
If you go bankrupt in Theme Park, the game shows a cutscene of the park owner jumping from a window while a family photograph fades, and Chopin's Funeral March plays. Though it turns out he was actually jumping out of a first-story window, as he turns around, grabs the windowsill, and pulls himself back up. As it was a game for all ages, even joking about suicide was pretty controversial. It even describes what will happen if you go bankrupt in the manual. It's actually pretty creepy; watch at your own risk.
The Mega Drive/Genesis version contains only a still image of that scene, which happens to be the park owner in mid jump.
Kohaku in Tsukihime in Hisui's route. The True End she succeeds. The Good End Shiki saves her at the cost of some of his lifespan. Either way, she points out that she has nothing left to live for anymore and did not really want to do what she did.
Erica in the backstory for Malicious, she was weak and frail, the girl was in the middle of a grand scale war started by her own father King Eldrake, the tyrant corrupted his own kingdom and had his wife, Queen Ashlelei, imprisioned. When Erica and her brother freed their mother to start a revolution, Eldrake started an alliance with barabarians, in the battlefield Erica could not fight so she choose to hurt her father by killing herself in front of him, to no avail as King Eldrake felt not remorse at the sight of his daughter taking her own life before him.
The second Oddworld game has several kinds of Mudokons working as slaves for the evil meat-making corporation. Inbetween others there are hyperactive ones who you have to slap to snap them back to sanity, and depressed mopey ones who need to be cuddled to bring up their spirits. But slap a depressed one and watch as he goes over the edge, and repeatedly hits himself in the head until he dies.
Intentionally done to the local priest, Minase, in Suika. And he deserves it too. First, he strangled his insane wife to death, which... might be overlookable since she was nuts. But then he comes across his daughter Itsuki, kills her with a shovel and buries the two together. He puts his other daughter Sayo, unconscious and badly bleeding after Itsuki herself threw her down a flught of stairs, in the hospital and doesn't even recognize which of the twins she is. When Akira finds all this out, he confronts him and recommends suicide.
In the The Thing video game, if your teammates get scared enough, they will pull out a pistol and shoot themselves in the head.
In Resident Evil Outbreak, certain members of your team will commit suicide if they have a gun and have been cornered by zombies or have incurred too much damage. Also, in the first level, you can recruit a sick (infected) security guard named Bob; if you help him up to the roof, he says something akin to the hunger being too painful and that he can't go on, then blows his brains out.
This happens if you scare the teddy bears enough in Naughty Bear.
At the end of Toshiko's series of missions in Grand Theft Auto: Liberty City Stories, which she has Toni perform against her husband Kazuki in revenge for neglecting her, culminating in his death, she realizes that she has lost everything, and commits suicide by defenestration as Toni watches.
In Obs Cure II, Kenny drives Corey to kill himself right before the Final Battle, just to twist the knife.
The ultimate fate of Priscilla and Raven's parents, Lord and Lady Cornwell in Fire Emblem 7. For worse, Raven believes they were murdered, thus fueling his Revenge.
Also, it's hinted that Ninian and Nils seriously considered killing themselves at some point, driven into despair after being summoned, captured and hunted down by the Black Fang. Thankfully, they don't go through it.
Someone killing themselves is actually a plot point in Fire Emblem Awakening. The dead person is Chrom's sister Emmeryn, who throws herself off a cliff to avert a war between Plegia and Ylisse that would tear the world apart. This selfless Heroic Suicide raises the Ylissean cause and causes almost everyone to desert Gangrel, the King of Plegia. Subverted later: Emmeryn is found to have survived (though at the cost of suffering Trauma-Induced Amnesia) and can be recruited as a playable character.
In a more traditional manner, Henry commits suicide in his ending if he's unmarried. Then again, it's Henry we're talking about, so no one (even in-universe) is surprised.
Late in Valkyria Chronicles II, when the Rebels actually succeed in completely taking over Gallia, the sheer hopelessness of the situation causes Lanseal's headmaster to have a mental breakdown that ultimately culminates in him shooting himself in the mouth.
Shadow Warrior has a humorous version: the standard mooks that shoot Uzis at the player character seem to have a high enough sense of honour that they'll take their failure to kill him in the only way a honourable warrior would: by eating their gun and shooting half their skull off.
Mamiya Shinzo commits suicide out of guilt and possibly as atonement in several endings of Kara no Shoujo, possibly after killing his son Shinji, who is the second serial killer.
Claus, aka the Masked Man, commits suicide by reflecting a lightning attack off of Lucas's Courage Badge at the end of Mother 3. Shortly after he came to his senses.
Because of a certain split-second image in a certain scene in Luigi's Mansion of all games, it is speculated by some that Luigi may have committed suicide and that his appearance in said game is him as a ghost.
In Demon's souls, mistress Astria will be kill herself, only if you manage to kill her loyal guard first, and considering the game it's actually the easier path as it's only him, becoming an Anti-Climax Boss depending on how you take out the guard, you can wear enchantments and stand just out of his sight of you and make a cloud of poison to slowly kill him.
Also, Ostrova, son of the king, will be driven to this no matter what, if you don't kill him first anyway, and you have to face his vengeful/sorrowful spirit a second a later, people's bad side being able to materialize as black phantoms, actually just dark red with a black motif.
In Sword of the Stars, Liir Black Swimmers who have had to put enemy civilians to the torch usually pilot their spacecraft into nearby stars after hostilities conclude.
In Hatoful Boyfriend it is revealed that Nageki killed himself five years ago. The full version gives context, and it's rough.
In Katawa Shoujo, it's all but stated that Rin Tezuka might end up doing this, since in her route she becomes more and more self-destructive in her despair to get enough inspiration to create art, which does not mix well with how she cannot exprress herself unless it's through art itself. Also, that same route says that the husband of her sponsor, Sae Saionji, was a talented artist who also committed suicide, for exactly the same reason.
Something that's kinda overlooked by fans during early playthroughs is that Shiina Mikado aka Misha also has suicidal tendencies. In Shizune's route, during a talk with Hisao, she tells him "Wouldn't it be better if I disappeared...?"
In the beta to the game, Misha would have committed suicide if you-as-Hisao took the Sex for Solace offer. She would've run in the path of a speeding car after a last talk with Shizune, if you wonder. And for worse, Hanako's bad end would've had her throwing herself in front of a train in front of Hisao.
To make matters worse, Shizune could commit suicide after Misha's death. She'd become depressed and lock herself in her room . One day you get a call from her brother Hideaki saying she's in the hospital due to dehydration. After you leave the hospital you learn she died a few hours later. She refused to sign to you so you wouldn't notice the IV she had pulled out, or the mess it was making.
In the 2012 reboot of Syndicate, it's possible to hack other people's DART chips to force them to kill themselves.
Dead Rising 2 has Brandon Whittaker, who slits his throat with a shard of glass after getting bitten by a zombe he kept in a bathroom stall to "spread the goodwill",, Leon Bell, who lit himself on fire for quadruple points rather than get killed by Chuck, and Amber or Crystal Bailey depending on which one you killed.
Fairly late in The Way 2, the main character comes across a guy threatening to jump off a cliff. Given the proper dialogue choices, you can talk him down or convince him to jump, or, if you're feeling really cruel, push him off yourself.
Konrad in Spec Ops: The Line, and Walker in several of the game's endings. Adams is last seen making a likely-fatal Last Stand, and seems in no doubt that he deserves to die by that point.
Sakura Oogami from Danganronpa, as a way to release herself from Monobear's blackmail of her without having to murder any of her classmates.
The concept of freeware puzzler Karoshi is that the player character has been driven to suicide, and the goal is to kill him to advance to the next level.
A major plot point in Virtue's Last Reward is a disease that causes infected individuals to try and kill themselves. In most timelinesQuark is the first to attempt to kill himself, however it's Alice that's the first to go. The player character also does this in Clover's ending, though whether or not it was a result of the virus is debatable.
In one of the secret endings of Arfenhouse 3, Licorice Guy, the arch-nemesis of Candyland, throws himself over the waterfall, overcome both by the shame of having killed his mother there and by the realization that he's in an Arfenhouse game. Joseph, tired of being the Only Sane Man in the party, then decides to follow his example.
In Bioshock Infinite human enemies hit with the possession tonic will kill themselves when it expires, often in gruesome and shocking ways while recounting some sin.
In Remember Me, one of Nilin's memory remixes makes Forlan believe that he killed his wife, causing him to commit suicide.
In S.T.A.L.K.E.R.: Call of Pripyat, if you manage to solve the mystery behind the missing stalkers in the first map, you'll find that The Medic from the main wrecked ship was responsible for their deaths. He explains that he used to work in a surgeon's clinic and became terrified of seeing his patients undergo gruesome procedures. Over time, however, he developed a clinical condition that causes him to crave the taste of blood and made him lose his sanity. When he came to the Zone, he snapped from the inside and started to secretly murder stalkers when they least expected it and disguised them as bloodsucker attacks. After he tells his story, he guns himself on his chin. However, you can avert this by shooting him yourself, though you have a couple of seconds to do it before he offs himself.
In Persona 2: Innocent Sin, the heroes meet a ghost of a teacher who threw himself into the gears of the school's clock tower. Officially it was ruled a suicide, as he had just gone through a very acrimonious divorce and was showing signs of depression. His ghost says he was trying to prevent the end of the world, having interpreted an obscure prophecy as alluding to the clock signaling the beginning of the end, and he thought that if he killed himself in the tower the school would turn it off permanently. It was a little of both and then some, because he was haunted by the Big Bad, had his life ruined, and finally at the end was given a little "push."
In RefleX, Raiwat commander-in-chief Tsukikagerou is so utterly ashamed of failing to capture the ZODIAC Ophiuchus and being forced to retreat that he kills himself.