"It's like you touch the top of the building, you die, you touch the ceiling, you die, you touch the floor, you die, too far to the right, you die, too far to the left, you die, you die, you die, you die, die, die, die, die, die, die, die, die, die, die, die, die!!"
A character who dies from a single hit or other incident of damage. Needless to say, this rarely applies to bosses, unless they are of the Zero-Effort variety. In older video games, this was frequently true of the protagonist; nowadays, the Player Character is usually only a One-Hit-Point Wonder if the programmers/developers want the game to be Nintendo Hard.
As mentioned above, this is more common in older games (especially the Golden Age of Arcade Games), and part of what makes a game Nintendo Hard. Modern tactical shooters also use this feature as well, even if Instant Death Bullet itself also grates on the "realism" bit.
Some games will give the One-Hit-Point Wonder access to shields or other powerups that allow them to take extra hits, but they still count as examples of this trope, provided that the character does not start off with said method of taking an extra hit.
In some cases, this creates the bizarre effect of giving the Goddamned Bats more health than the player.
Rocket Tag Gameplay have everyone in this situation, so that whoever manages to hit first will win.
Has nothing to do with a One Hit Wonder, although it is sometimes referred to as such.
While not a Mario offshoot, Commander Keen was designed with Mario in mind, and the title character is just as vulnerable. One hit and the Defender of Earth is dead. Ditto Dangerous Dave, another early John Romero game.
Hexers can become this in Etrian Odyssey, if you try to maximize the damage for their Revenge skill—255% of the damage they've taken will be dealt to the enemy, but the Hexer will not survive a single blow.
In Ultima Underworld II, Krilner the Coward is a character who only has 1 hit point. You can confirm this by casting a certain spell on him to read his statistics.
The Pokémon Shedinja is a unique example of this in a game that doesn't usually use it. While lifebars do exist in-game, Shedinja only ever has a single hit point, making its own life bar rather pointless. It's kept from being a novelty Pokémon by its ability, "Wonder Guard", which protects it from all damage that isn't super effective. Nonetheless, the first attack that damages it defeats it outright (see The Law of Diminishing Defensive Effort). It's also completely vulnerable to indirect damage (including damage from things like Standard Status Effects, recoil, weather, Spikes)... really anything but regular damage. Still, it gives Shedinja the odd honor of being not so useful in the standard metagame (due to the popularity of entry hazard Stealth Rock), yet fairly useful in the Ubers metagame, where few Pokémon even carry anything to KO it.
In Doubles and Triples, it's possible to change his ability to Sturdy. This is useful because in Gen V onwards, it acts exactly like a Focus Sash: the Pokémon is guaranteed to survive a lethal attack with exactly one hit-point as long as it has full life, the difference being that Focus Sash stops working after one hit, but Sturdy doesn't. Because Shedinja only has one hip-point to begin with, it will always have full life, from EVERY attack. The only way to kill it is status effects or weather.
Plus, any powerful Pokémon with a Focus Sash or Focus Band can survive a would-be fatal hit with exactly 1 HP. With enough luck, a powerful enough Pokémon can sweep through an entire opponent's team with just 1 HP. Blaziken and Heracross are the most known for this, gaining a bonus on an attack called Reversal that hits harder the lower your life is.
Some tactics turn a 1 HP Pokémon into KO-ing machines. Like Magikarp, or a Level 1 Rattata. No opponent worth his salt will fall for it, but it's still funny to see Level 1 Rattata banned from tournaments. Now that Sturdy acts as a Focus Sash, people now run a level 1 Aron with Sturdy, Endeavor, and a Shell Bell in a sandstorm. Sturdy prevents Aron from going down in one hit. Endeavor takes the foe's HP to equal the user's. Shell Bell restores 1/8th of the damage dealt by the holder's attack, so when Aron uses Endeavor it will heal up to full health so Sturdy will work again. Shown in this video.
1943: The Battle of Midway (and in the 90's, the sequels 1941: Counter Attack and 1944: The Loop Master.) gives you a life meter, but do note that these games give you just one life - lose it and it's game over.
1942 Joint Strike gives you a life meter and multiple lives, but no continues.
Gauntlet (Atari Games) and Dragon Buster (Namco) were among the first arcade games to have a Life Meter system (though in the former, your health was displayed numerically, rather than as a bar, although the latter had both). Later, Rampage had a Life Meter as well.
In Crazy Climber, a falling object doesn't kill you if both hands have a secure grip. (It dislodges one hand.)
Some games allowed you to take two (or more) hits before dying. Usually, the first hit destroys your shields/armor/whatever, and the second kills you. Arcade games of this type include Toy Pop, Ghosts N Goblins, Blaster, the Star Wars and Star Trek arcade games, and Black Tiger.
Some classic arcade games let you command multiple ships at once, or join ships into a more powerful ship. Each ship was a One-Hit-Point Wonder, but losing one ship didn't end your turn if you had another. The most famous is Galaga, but Space Duel, Moon Cresta, Eagle, Tac Scan, and several Galaga sequels also worked this way.
The arcade version of Rolling Thunder has a life gauge with eight hit points, but it's nothing more than a cruel joke. A single touch by an enemy will reduce the player's life gauge by four points, while enemy bullets and laser traps will kill him instantly. So in reality, the player only has two hit points. The NES port and the sequel had a more honest representation of the player's health, while in the Genesis-exclusive Rolling Thunder 3, the player actually has three hit points on the Normal difficulty (allowing him to survive at least one enemy bullet per life).
Bushido Blade is that rare Fighting Game where both you and your opponent are a One Hit Point Wonder... at least in theory. In practice, only a couple of moves had this quality, and it usually took a few hits before the lethal blow.
Karate Champ on the Nintendo Entertainment System also has this, in order to keep things more realistic... except it's the match or round that is over when you hit or get hit by the opponent... but not the opponent himself.
The original Way of the Exploding Fist had this too, but it was emulating traditional martial arts tournament style, where any telling blow ended the round with a point for the striking opponent.
Most games in the Rainbow Six series use a variation. It only takes one solid hit to incapacitate a character — and, in the single-player campaigns for your team, possibly kill them, permanently removing them from the game. Less solid shots, such as to extremities, take two hits instead, and hamper the target on the first hit. Ghost Recon works much the same way.
Operation Flashpoint also plays this one in a similar way; as a result, there's not even a health bar.
However, not every hit is always fatal: depending on where the player is hit, it may make him unable to stand up and run normally (if hit on the legs) or render the aimpoint extremely wobbly (if the arms are no longer healthy).
The game handled this in an interesting way. A hit on a certain part of the body would have a percentage chance to kill and a percentage chance to injure. For example, a headshot had 99% chance to both kill and injure, whereas limbs had 30% chance to kill and 85% chance to injure. This means that while any shot can kill, and most shots will injure, it is theoretically possible to survive a huge amount of gunfire (although highly unlikely). Large explosive weapons, like tank shells, which hit every body part with splash, would almost certainly kill.
The "Heaven or Hell" difficulty in Devil May Cry 3 grants this quality to every single character - Dante and all of his enemies. Yes, even the bosses. What makes it tricky is that Dante can die from taking damage off environmental obstacles, which of course do nothing to enemies. And then there are some enemies which need to be struck at a weak point, whereas Dante has no such advantage.
"Hell or Hell" mode in the fourth game plays this the traditional way, although to compensate for it, you get a stock of 3 Auto Revive items to help you that are replenished whenever you reach a checkpoint.
Most early Bomberman games made the titular hero a One Hit Point Wonder. He can survive one hit if he has the "Heart" power-up, which acts as a shield. Starting with the Nintendo 64 era, Bomberman got a lifebar.
What makes this funny is that he could be one-shotted by bumping into balloons, of all things (Granted they are cute monster balloons, but still...), making his case very obscure.
"Standard" mode in Act Zero plays like this, with the added condition of only giving the player one life to go with it. Should you get hit by any bomb blast (including your own) without a shield, your game is over (made extra-frustrating because the single-player mode is very long, and the player is not provided with any continues or save points of any sort — got killed on level 98? Back to level one for you!).
A late mission in Zone Of The Enders sees Jehuty's AI Ada infected with a virus. While in this condition, any kind of damage will instantly destroy Jehuty, forcing the player to resort to sniping enemies from afar or risk a game over.
The Eric Chahi game Another World (known as Out Of This World in US) worked this way. Some combat elements, such as the blaster pistol capable of creating blaster shields, made it rather complicated to get through certain firefights, almost qualifying it as a Puzzle Game. The unsuspecting player is in for a surprise if he tries to run past the worms crawling on the ground in the first area.
Lampshaded in the Fan SequelI Wanna Be The Fangame, where the Kid is brought into a Pokémon battle screen, and his Life Meter starts at 1/1.
Speaking of Castlevania, Haunted Castle version M on default settings comes close; two hits from a skeleton's bone throwing attack will kill you.
There is also a way of becoming a One-Hit-Point Wonder in Castlevania: Circle of the Moon - use the Black Dog and Pluto DSS cards together and you turn into a skeleton. However, while in this mode, one attack will kill you.
The advantage of this mode is that while Up + B will usually throw a skeleton bone, randomly it will throw a big skeleton bone. Anything it comes into contact with - mook, boss, whatever - gets a guaranteed 9999 damage, thus turning them into One-Hit-Point Wonders.
Final Fantasy VI actually plays this trope the other way around at one point. About halfway through the game, you will be controlling one character on a small island. The random battles consist of two monster types that have a single hit point each. On top of that, they start the battle with a HP Sap effect, meaning they often die before anyone gets a turn. They're almost completely useless for anything but decursing an item that requires you fight 255 battles with it equipped, but you can steal Elixirs or Megalixirs from them if you're fast enough.
They do have one extremely useful benefit; if Gau ever ran into them in the Veldt (where almost every enemy in the game would reappear), he could imitate them. If Strago was in the party when Gau did so, he could learn a couple Game Breaker spells (like Mighty Guard, which made boss battles a complete joke).
However, it's also possible to be afflicted with Zombie status on that same island (there's a formation of monsters in the desert that doesn't belong to this trope). Since Zombie makes your character uncontrollable, and you'll only have that one character at the time, you're potentially a One-Hit-Point Wonder until you get off the island. Or until you equip a Ribbon.
The monsters, should they get a chance to hit you, do about average damage for this point in the game. So despite the lameness of their HP stat and their Seizure status, they can pose a challenge for a Level 1 character.
In the NES version of Dragon's Lair, the player actually has a life bar, but most hazards in the game kill him instantly, such as touching a stationary, ordinary door. In fact, the ONLY two enemies in the game that do not spell instant death are the bats and the skulls. Why did they bother?
Averted in Dragon's Lair 3D: Return to the Lair, where Dirk not only has a life bar, but he also has mana and can take some hits from all enemies before dying, though Bottomless Pits do spell instant death.
In Mega Man Battle Network 5, Megaman can keep corrupting himself with Dark Chips (Each use of them subtracts 1 of his max Hit Points) until he becomes a literal One Hit Point Wonder. Though the enormous firepower of Dark Chips is enough to say the same about most enemies, if not bosses.
In the Delta Force games, you can only take one, maybe two shots if you have armor. However, the enemies also can't take more than 1 high-powered shot, even to limbs (which is more realistic than other games, if you think about it), and they tend to be uninteligent, relatively stationary, and terrible shots.
The shmup / RPG hybrid Sigma Star Saga is an odd example. Your character has a lifemeter, but the animation for getting hit shows his ship exploding and a new one flying in from offscreen, like in most shmups.
Averted with the onset of a two hit wonder: a boxy-carrier. One hit causes it to crack open and fall apart, revealing a small and nimble warship.
It is justified/handwaved by the plot: The Alien Empire for which the hero works has enough resources to build countless living ships but is lacking decent pilots, so the pilots are teleported from ship to ship and can sustain the teleportations.
The old Sega Genesis/Megadrive game Ristar featured this. The highest (secret) difficulty level not only turned the titular character into a 1HP Wonder, but also a One-Life Wonder; one touch is literal instant death, and all health and 1ups are converted to gems. However, as compensation, the game gives unlimited continues in this mode, meaning death only sends one back to the start of the level.
In La-Mulana, if you equip the F1 Spirit 3D and Contra ROMs (in that specific order), you will die after taking one hit. This is in stark contrast to the latter half of the game, where you will probably have so much health that dying becomes completely irrelevant, except against a boss. (Ironically, the Contra ROM is for the MSX2 version, which averted this.)
Ice Climber had many strange creatures and things kill you in one hit, such as the Topis, falling icicles, and a polar bear with pink shorts and sunglasses! No, really!
The very first Grand Theft Auto game had anything that was harmful kill you in one hit. Body Armor let you survive up to 3 bullets though.
Win Back featured an unlockable "Sudden Death Mode" wherein a single bullet was all it took to send you or any enemy to an early grave. Amusingly, this led to encounters with simple guards becoming white-knuckle standoffs, while most boss characters wound up on the floor before they even finished taunting you.
On the last level in Combat School, you have a life bar, but everything in the level (being shot, touching an enemy, touching something on fire, etc.) kills you instantly. Except the final boss, whose hits aren't fatal — so that's what the life bar is for...
The ninja in N: The Way of the Ninja is about as flimsy as wet cardboard - there's an X-Box Live achievement which requires you die 2,000 times in the single-player mode. It's easier than it sounds.
One More Extra Stages in Dance Dance Revolution force you to play with the "Sudden Death" modifier; if you get one Good, Bad, Miss, or NG, you instantly fail the song. The same applies to Dance ManiaX 's Extra Stages. DDR's Oni/Challenge mode is like this as well, but you get three chances to screw up before the fourth fails you, and you get a chance back after clearing certain songs.
The normal Extra Stage in Dance Dance Revolution SuperNOVA 2 could be anywhere from this to a four-hit-point-wonder, depending on how well you did on your final stage. DDR X ups the minimum to two instead, but the maximum is still four. Considering some of the songs are loaded with Fake Difficulty (Pluto on the CS version being a major offender - stops are less predictable than CHAOS from DDR SuperNova), you're kinda screwed.
pop'n music's Cho-Challenge mode has the DEATH norma, which when activated will cause a miss to wipe out your life meter. However, this doesn't end the stage; you just have to rebuild your life meter all the way back up. For extra fun, activate the "COOL or BAD!" norma, which removes all timing judgments except for COOL and BAD, so if you're outside the timing window for a COOL...
Guitar Freaks and Drummania have the Risky option. If you turn it on, you can set it to 1, 2 or 4 before the song starts, then if you get that many POOR and MISS judgments combined, you fail instantly (but unlike other Bemani games, you can play out the rest of your songs, although you can no longer earn the Extra Stage).
Dance Dance Revolution X2 also added a Risky option. When turned on, you get the One More Extra Stage life meter, but you can play out the rest of your songs even if you fail.
Original edition of Knights of the Sky, WWI-style air combat sim from 1992, had 1 HP planes (including yours, of course). To be honest, their real counterparts were not much more durable either.
Three of Apogee Software's early CGA games: Arctic Adventure, Pharoahs Tomb, and Monuments Of Mars. One hit from anything would mean losing a life
Not to mention that to run the game faster, enemies are circumscribed by their hitboxes to simplify collision detection, so you had to compensate for invisible death-squares around every bad guy. The game even calls this "F.A.S.T. technology" and brags about it in the instructions.
Although you typically have several lives in the conventional Touhou games (starting with at least three), in the First Person Snapshooter games Shoot the Bullet and Double Spoiler, one hit will end the game—that is, end the scene in which you're playing. There's nothing more soul-crushing than taking 9 photographs on a 10-photograph scene and then dying as your camera zooms in to take the last one.
Similarly to Super Mario, Sonic the Hedgehog is a One-Hit-Point Wonder, except when he has at least one ring on him, or a barrier.
Having multiple rings, unfortunately, is no more effective in terms of protecting Sonic than is having only one ring.
Sonic Chronicles, an RPG-style game that uses HP bars, has an example, interestingly enough. It's the final boss battle against Imperator Ix, when both he and Sonic are in their Super forms. If you don't flawlessly execute your Action Commands and take him out in one turn, he regenerates his HP and you have to try again. Fortunately, Ix has the same problem, so as long as you can do "good enough" at the Action Commands when it's his turn, you can keep going as long as you have the patience.
Shining Force has this in the form of Jogurt, who has exactly one point in every single statistic. Though his hit points can be raised through items.
Jogurt was largely a Self-Imposed Challenge, though successfully defeating an enemy with him awards you with the Jogurt ring, which doesn't do anything but change the sprite of another character into Jogurt.
It should be noted, Jogurt has 7 movement, which is higher than most characters. Still, since you can't boost any of his stats nor level past 1 (other than by equipping Rings... leaving him still doing effectively 1 damage), he's still the most useless character. Unless you want to work super hard to earn lots of Jogurt Rings to sell for 'unlimited' chump change (less than earned from the defeated enemies...).
Gaiares, at least until you get a shield, then your a 6-or-so-hit-point-wonder. unless you die on the final stage, which has no such shield item, which is one of the reasons why that stage (which is ONLY a boss fight) is That One Boss. Oddly enough, your TOZ can block some bullets.
The Glider games would make you lose a glider if you hit almost anything that wasn't a prize. Having aluminum foil in Glider PRO would shield you to some extent, but foil wasn't a guaranteed find and would be hard or literally impossible to keep.
In Gradius, if you don't have a force field, the only things your plane can touch without blowing up are power-ups.
Genzo from Daiku no Gensan in the original arcade game and Hammerin' Hero. In most of the other games, he does, in fact, have a health bar of some sort... but in those games, he's down in one hit unless he has a hard hat to absorb it.
Metal Slug characters die in one hit from bullets, melee weapons, or getting run over by a tank. Unless you pick one particular character in Metal Slug 6.
If Harder Than Hard mode examples count, player aircraft in the Ace Combat go down with just one missile hit when played on the highest difficulty (except in X: Skies of Deception where a high enough defence allows you to get away with 90+ , maybe 80+ % damage taken... not that many planes are both that survivable and still good dogfighters). Enemy aircraft, on the other hand, remain just as durable as on normal difficulty.
LittleBigPlanet has Sackboy, who basically explodes if he comes in contact with any of the various hazards in the game. The exception is fire, which he can bounce on once before being burnt to a crisp.
It also has Scaramanga's gun (from The Man with the Golden Gun), which is a weapon that basically turns the entire world into One Hit Point Wonders, because it instantly kills anything it hits. If you know your Bond, you'll know this is because Scaramanga was such a good shot, he never needed to shoot anyone twice. In the game, even shooting someone in the foot with it will instantly kill them, but the gun has only one bullet. There's also a golden PP7, which acts like the golden gun, but with 7 bullets.
Though it wasn't programed as "this gun kills everything in one hit." It was programmed as "this gun does a lot of damage". Play with max health handicaps and a body armor pickup. If they shoot you in the foot, you live. A torso show will still kill you, though. Also, Janus is immune to the effects of the Golden Gun. Janus can be killed from the golden gun on the last (non-bonus) level if you shoot him during one of the windows when he's vulnerable.
You could also play with no guns in license to kill mode with everyone running around judo chopping. This essentially turned multiplayer into a game of lethal bumpercars mixed with a The Benny Hill Show sketch.
In the Deadly Rooms Of Death series, the player and everybody else has one hit point, with the exception of very large enemies that shrink when you hit them (snakes and the rock giant). In addition, some enemies can't be killed with any of your own weapons. Added to this that it is a turn based tactical game with tiny turns, to the point of being a puzzle game, and it was designed by a bunch of total sadists, the series is one of the hardest around. DROD RPG uses HP for the player and the monsters, and employs deterministic statistic-based combat mechanics, which also cause a need for difficult strategizing.
In System Shock 2, if you play on Impossible difficulty as an OSA operative, you start with 10HP... which is coincidentally the exact amount of damage done by the very first enemy you encounter, a pathetically weak (on any other difficulty) pipe-wielding parasite zombie. While there are enemies that deal less damage, the fact that you're a one-hit-kill at the very start of the game means that the Impossible OSA path definitely qualifies for this trope.
Jumper series takes this trope, uses it, loves it, becomes one with it. It also does the same with Malevolent Architecture and becomes many times harder because of the most evil game mechanic known to man — the golden arrows, which allow you to make more than one Double Jump in midair. This leads to aerial "jump mazes", usually completely surrounded by hazards, requiring pixel-precise jumps to pass it. Yes, it's as hard as it sounds and, yes, this is part of the fun.
You can still survive being shot with machinegun fire and hyper pulse. The good news is that enemies has the same health as you, even bosses.
Your units in X-COM actually have life bars but, until they are experienced and get armor (and it takes a while), for practical purposes they might as well be one of these. The health bars average between 40 and 60 health points, and the weakest alien weapon (Plasma Pistol or Sonic Pistol) does 80 damage. An extremely lucky soldier will survive a single hit, be knocked unconscious from the pain, and then die the following turn from bleeding out. Apocalypse actually tends to avert this trope, however, as your soldiers start with basic armor that can actually resist a few shots.
In Ratchet & Clank: Up Your Arsenal, while you had hit points in the rest of the game, one of the deathmatch types at Annihilation Nation, appropriately named "One Hit Wonder", forces you to kill waves of enemies without taking a single hit.
Going Commando, the previous installment, had a similar gametype available in its arenas. Ratchet didn't die, per se, but he did have to start the round over if he wanted credit for completing it (and he would, naturally, need to buy new ammo).
However, in these games you have access to energy shields which allow you to take hit(s) before losing these challenges.
In the first two Oddworld games, anything (including the player character) could be killed by anything else with one hit. Unless they're being slapped or licked. That takes more hits.
In An Untitled Story, completing the game on Masterful difficulty unlocks Insanity Difficulty. Technically, you start with 100 HP and can get over 1000 if you collect all of the hearts, but everything deals so much damage that you die in one hit whether it be the Final Boss or a simple snail.
T2 The Arcade Game has the level after Cyberdyne in which if the T-1000's police helicopter rams into the protagonists' SWAT van even once, the player has to start the level over. Definitely worse than That Truck Level.
Course, the helicopter was itself something of a one-hit wonder, as far as deflecting the attack went. Whereas that damn truck...you knew where it was, but good god, it was hard to stop.
Jumpman (later renamed Mario), from the Donkey Kong arcade game. Not only will he die from touching one of the various hazards (barrels, spring-things, fire, pies), he'll also die if he falls several feet.
Donkey Kong Junior doesn't fare much better.
Jumpman, a game for the Commodore 64 not related to Mario, is like this as well. Getting hit, jumping or walking off a ledge, climbing into solid wall, and a few other things are instant kill. Just don't set run speed to 01.
All three Donkey Kong Country games, although if you have your friend then you switch to him/her when you die.
The second game did have an example of a boss with only one hit. When you refight K.Rool in Krocodile Kore.
In Donkey Kong Country Returns, there is a Mirror Mode where Diddy Kong doesn't appear at all and Donkey Kong only has one heart instead of the normal two hearts.
An interesting example is the game My Hero for the arcade and Sega Master System. While during the level the titular hero as well as the mooks can be killed in one hit, the boss battles feature life meters for both the hero and the boss.
Alex Kidd. Except in Shinobi World, one hit from something and he turns into a ghost, floating to the top of the screen waving his arms with a humorous "mwoop mwoop mwoop" sound. The Narm almost stops you from being pissed off at being killed from one hit by making you laugh.
Dizzy in the first three games of the series. (In the second game, Treasure Island Dizzy, you only had one life, too. The fourth game, Magicland Dizzy, added a Life Meter, but some of the hazards - in most games including water - remained instantly fatal.)
Jackal. Apparently being hit by a single bullet will destroy a jeep, every time.
Crash Bandicootlives (Or rather dies) by this trope (at least in earlier installments), sure you can get Aku-Aku masks to take up to two extra hits, but those tend to be rare unless you die several times in a row between checkpoints (where you're then given a freebie mask upon respawning). Regardless, when Crash is by himself, he croaks at even the slightest contact with an enemy or hazard... even seemingly harmless ones like turtles and skunks.
The freeware platformer Poyo by Lazrael plays this completely straight, but balances it out because the stages are all pretty short.
The Shigurui difficulty level in Muramasa: The Demon Blade turns your character into this. Although to balance it out, any time you're not in a bossfight, Death Is a Slap on the Wrist and as long as you have at least 1 sword intact, you can block pretty much any attack and not die from it. You can also do it in midair during some attacks, making it seem that the character is casually shrugging off an attack that should've killed'em several times over.
Crystal Quest has no armor, but its sequel has five different types as powerups. Most only protect against one kind of hazard, leaving you a One Hit Point Wonder to everything else.
Spelunker is infamous as one of the easiest-to-die characters in video game history. If you don't jump or jump wrong when you get off the elevator, you die. If you step into a pit that's as deep as your ankles, you die. The obscure arcade and Famicom sequels averted this. The remake, Spelunker HD, makes earning extra lives very easy, because you're expected to die so much.
Bugs Bunny: Crazy Castle (an old Game Boy and NES game) has Bugs running around dozens of floors of a castle where the other Looney Tunes have been brainwashed or something, and running into one of them just once sends you back to the start of the level. Only two items can circumvent this: one that temporarily lets you walk through other characters and one that temporarily lets you walk through and kill other characters. Made worse in that some characters follow you around and a few float through walls and floors.
Every unit in DEFCON, quite realistically. How many torpedo hits do you think a sub can take? To balance this, the chance to hit is quite low.
This was done because the developers felt that tracking hit points for every single entity in the game would bog it down too much, so instead gave things varying chances to be hit.
The Risk debuff in Phantom Brave turns anyone into this: any attack, no matter how weak or strong, either kills them instantly or misses them. Quite annoying when a randomly-generated dungeon gives this debuff to a roomful of enemies that you would one-hit kill anyway...
Sly Cooper was another example of this, even though you could get up to two horseshoes to withstand additional hits. The sequels actually gave you a health bar, though.
Kingdom Hearts II's gummi ship minigame has one of these. Your reward for getting 100% completion on all levels is the Crown/G gummi piece, which, when equipped, starts you off in "berserk mode". The catch is that you become the embodiment of that trope.
In 358/2 Days, equipping the Extreme ring sets your HP to one, but gives you infinite use of Limit Breaks.
re:Coded has an unlockable cheat that makes everyone into an example of this trope.
The classic Atari videogame Star Raiders, the ship goes down in one hit from an asteroid or enemy photon. Fortunately the ship's energy can retain a shield which changes hits from fatal to merely damaging some key component of your ship (at easier levels, there's a chance it won't even hurt). The shield itself is a damageable component, so you are at least two photons away from death.
Almost every enemy in the Time Crisis series can be killed with one shot anywhere, including the finger.
Final Fantasy Fables: Chocobo's Dungeon has optional mind zones where both you and monster's max hp are dropped to 1. The latter stages are even worse since it only your max hp which is set to 1 while the enemies have more HP than you.
Probably the Ur Example of this trope in video gaming was the 1961 game Spacewar! which was created for the PDP-1 computer, and which had its players dueling each other while maneuvering in the gravity well of a star. If you got hit with a missile from the other guy or hit the star, you were dead. There is only one PDP-1 still in existence, though the game has been ported to numerous platforms ever since.
The arcade machine in the cantina segment of Starcraft II has the game Lost Viking, a Bullet Hell type shooter. Although you can gain power ups to give you additional "health" you are usually will die to one hit of anything.
Grabbed By The Ghoulies gives you a life bar at all times, but will change the number of hit points you start with on a room-by-room basis, and several rooms give you only 1. Usually however, these rooms will come without a prescribed challenge besides reaching the open door on the other side, with only a small number of low-level enemies to evade if any at all. Not always, though.
There is also a trick power-up that temporarily reduces your health to 1. It will return to its previous total in a few seconds if you can survive.
In the DJMAX Portable series, as well as DJMAX Trilogy, some missions have you clearing a song or set of songs without missing a single note; instead of allowing you to continue having failed the mission, the game simply throws you an instant Game Over. There's also one particular mission in DJMAX Portable 2, "Just 1%", where getting a MAX 1% (the lowest judgment you can get from hitting a note) is an instant game over as well. DJMAX Portable 3 offers modifiers called "1 BREAK: GAME OVER" and "1%: GAME OVER", which have the same effects.
In Galactic Civilizations II, it is possible to design a ship armed to the teeth but with just one HP. This is accomplished by using the cargo hull as the base. This is usually done out of desperation in the early stages of the game in order to fight off a much stronger enemy (like the Dread Lords) until you can research bigger and stronger hull types. The ship usually will be destroyed but may deal significant damage to the enemy. Combine a few of these in a fleet, and you got yourself a disposable armada. Granted, the costs are higher than those of smaller ships, but desperate times call for desperate measures. Also, putting defenses on these is usually pointless, unless you can put more defenses than the enemy has firepower.
Non-video game example: In the 4th edition of Dungeons & Dragons, there's a "minion" class of monster who basically has the same stats as a normal NPC/monster of its type, but only 1 hit point. They basically have two purposes: to give the PCs a horde of easily dispatched enemies so the players can feel all Bad Ass, or to run interference for a more powerful enemy.
In the earlier games, it was quite possible for a first-level player character to be this. First-level magic users were especially prone to being this due to having the smallest hit dice in the game and their inability to equip any armor, leading to a tendency to die if an enemy so much as looked at them funny. This was partially fixed in version 3.5 with the rule that all characters get their maximum hit die roll at first level.
Duncan died in one hit from anything in the first Dark Castle. Beyond Dark Castle combine the level timer with a Life Meter to allow Duncan to survive some hits at the expense of time.
In FAST Racing League your vehicle can only hit any obstacle once before turning into a flaming wreck. Strangely this does not apply to hitting the course walls or other racers, who do no damage, only to flying to the side of the course, hitting walls set to block off your path or running into the flamethrowers which all kill you instantly.
Hard mode for Metroid: Other M. You only start with 99 energy (one Engergy Tank) and 5 Missiles; all extra Energy Tanks, Missile Expansions, and Accel Charges are gone. By halfway through the game, most enemies and bosses will do more than a whole energy tank's worth of damage, killing you in a single strike. Good luck fighting the Metroid Queen this way.
Thank goodness they added the checkpoint feature, so you don't go all the way back like most games, as well as the Sensemove dodge (completely avoid damage, similar to Smash Bros.). Not quite as Nintendo Hard as it otherwise would be, but still extremely hard. Of course, some attacks get past Sensemove (such as Metroid Queen's flames) by having simply too large/lasting of hitboxes to avoid.
Also, probably nice that you don't have the Extra Final Boss, Phantoom, in Hard mode. It's near enough to Nintendo Hard with all expansions, but trying it in a OHKO situation? Sure, it'd be neat and bragging rights...
Spyro the Dragon, in the original games at least, should count. Without Sparx, one hit and he's a goner.
The eponymous chick in Toki Tori dies in one hit from an enemy or spikes. Since the game is a Puzzle Platformer, it is mandatory to find out how to avoid the monsters; avoiding them is the easy part.
Chelnov from the Megadrive/Arcade game Atomic Runner is probably the wimpest example of this trope. Not only does any given enemy or bullet kill him, but so can the candles you obtain power ups from. So much for the Atomic Armor!
In case you thought the game wasn't Nintendo Hard enough, a special mode in Punch-Out!! makes you lose the match if you get punched even once. The only exception to this being Aran Ryan's rope-glove attack when you knock him down.
The "three-heart run" is a popular challenge with Zelda players. After the boss of each dungeon in a Zelda game, there is one heart container, which increases the player's maximum health. Eschewing these heart containers leaves the player with three hearts throughout the entire game, hence the name. However, enemies in later parts of the game might be programmed to take off more than three hearts per hit, in expectation of the player having enough hearts. As a result, if an enemy that takes off more than three hearts hits a player playing through a three-heart run, the player will die instantly. This is especially inconvenient when there are multiple enemies that do such damage in the same room, which could be common in later dungeons.
Every playable character in Rayman Origins. You can collect a heart powerup, which makes you able to take one extra hit.
In Aqua Rhapsody, if a single enemy touches the castle, the castle will spontaneously explode.
In The Fairyland Story, the only thing that hurts Ptolemy but doesn't kill her is the wizard's spell, which weakens her with the first hit.
The ball in Roll Away is inflatable and so is easily destroyed by heat, spikes and captivators.
Missiles in most of the X-Universe series will be destroyed by a glancing blow from the weakest gun in the game. The latest game X3: Albion Prelude gives them a health bar, however. Also, M5 scoutships are effectively this when faced with the flak guns on a capital ship, and in the first two games every ship was one of these if its shields went down (X2: The Threat added hull armor as a mechanic).
Averted in Doom, although played straight in Action Doom.
Inverted in Kung Fu Master; the player has a life bar but most of the Mooks go down in one hit. Also applies to Spartan X 2.
The Bucky O'Hare game for the NES had the player dying in one hit when playing on the hidden hard mode.
Ralph from The Adventure Of Little Ralph dies from a single hit from any enemy, unless he has a shield which allows him to take one more hit. This is justified in that Ralph spends most of the game as a young child, and in boss battles after the middle of the game, he turns back into a man and can take a large number of hits without dying. Then Ralph randomly turns back into a boy afterwards.
The protagonist of Hotline Miami is killed by a single hit. Doesn't help that the game is incredibly fast-paced. However, there are unlockable masks that allow you to take a few more hits than usual.
In Ghost Recon: Advanced Warfighter 1's Hard mode, all enemies aim for the head and thus kill in one hit.
Your car from Highway Hunter is this in Hard difficulty. The lifebar is replaced with a lives meter, life powerups are extra lives instead, and your weapon reverts to the V-Laser each time you're hit.