Just as characters can get stronger by killing things and leveling up, so too can their weapons. Absolutely no modifications are made to the weapon, they just get stronger over time. Which makes no sense without some kind of AppliedPhlebotinum at work. Usually justified with a LivingWeapon or EmpathicWeapon. It's occasionally [[HandWave handwaved]] that the weapon has a sort of [[VampiricDraining vampiric nature]], or that killing a certain creature for so long has made it more effective against them.

Having an evolving weapon allows the hero to carry it throughout extended lengths of gameplay without the weapon becoming obsolete and [[CantCatchUp underpowered compared to your hero]], thus making it a bit of a trademark of the hero and highlighting how awesome it is. By unlocking its powers bit by bit, you also avoid having a [[DiscOneNuke too good weapon early on]].

Alternatively, there is a second way this works. Instead of the power gain being permanent, sometimes it is only temporary. Maybe it unlocks some of the weapon's hidden abilities, or there might have been something special about what was just killed. Subtrope of EmpathicWeapon. Can serve as a FullPotentialUpgrade or keep that trope from occurring in the first place.

!!Examples of permanently evolving weapons

[[AC:{{Anime}} and {{Manga}}]]
* The Dragon Slayer from ''{{Manga/Berserk}}'' has become an anathema to Demons thanks to Guts relentlessly killing them with it for three years, to the point that even incorporeal beings can be hurt by the massive sword.
* In ''Manga/{{Bleach}}'', Ichigo's [[EmpathicWeapon zanpakuto]] Zangetsu keeps evolving since the ''Deicide'' arc. When he learns his ultimate attack, the form of his Bankai changed. Then, when Ichigo got his power back, Zangetsu's appearance changed completely in both, his Shikai and Bankai form. And in the current arc, when Ichigo knows the origin of his zanpakuto and gained his own asauchi, he got Zangetsu's true form, [[spoiler:a pair of a short sword and a long sword.]] Notably, it's only in Ichigo's case because zanpakuto usually don't evolve at all, they just have two released forms, Shikai and Bankai.
* In ''Manga/DGrayMan'', Allen Walker's [[EmpathicWeapon anti-Akuma weapon (his left arm)]] evolves over the course of the series. At the beginning, it's a gnarly, deformed red arm and all he can transform it into is a giant unwieldy claw. Thanks to a healthy dose of rage and HeroicResolve, it evolves and becomes capable of transforming into an ArmCannon and a LaserBlade. After gaining a greater understanding of his weapon and achieving a higher synchronization rate, [[spoiler:his arm becomes smoother and less disfigured, and his hand can transform into a much sleeker claw. He also gains body armor in the form of a cape, hood and mask. After breaking the critical point, Allen gains the ability to rip his entire arm off and transform it into a BigFancySword]].
* ''LightNovel/HighSchoolDXD'': [[EmpathicWeapon Ddraig]] explains this is the case for [[AmplifierArtifact Boosted Gear]]. Only its most fundamental property - doubling the user's power every ten seconds - is consistent for every wielder, its other abilities depend on the needs and personality of the one wearing it. In Issei's case, early examples are developing Boosted Gear Gift to transfer the power boost to more capable allies (compensating for the fact he starts the series woefully underpowered), and then a second gem on the gauntlet itself that glows when he has enough Boosts saved up to overpower his current enemy (allowing Ddraig to easily help Issei along when he's still no good at sensing magic).
* ''Manga/{{Inuyasha}}'':
** Inuyasha's sword, Tessaiga, explicitly has the ability to get stronger by killing things and gaining related abilities. [[note]]It has to be a strong opponent though. After mastering the Backlash Wave, all of the Tessaiga upgrades were based on this, one way or another.[[/note]]
** Bankotsu, another [=InuYasha=] villain, had a weapon called Banryu that gained demonic power after killing 1000 humans and 1000 demons.
* This is basically the entire premise of ''Manga/SoulEater''.
** Looking at what the Weapons can do to witches in the hands of meisters allied with Shibusen, one wonders what exactly Arachne was thinking. The 'Heretic' not only killed her fellow witches For Science (used the Book of Eibon to put into practice something that had never been done...for no clear reason), but gave one willing to wipe out almost her entire ''race'' for his own sense of justice (Shinigami might have fair reason, but his methods are questionable) a really effective way of doing so.
** Probably because the weapons are just as effective on ''anyone'', Witch or not. They just got [[GrandTheftPrototype hijacked by her enemy after she made the first few.]]
* The ''Anime/TurnAGundam'' has this going for it for several reasons, some being closer to this trope while others are a straight example of MidSeasonUpgrade. First, Loran uses the instructions manual to find out about all the Gundam's various systems. Two, the grit and grime that was inhibiting its power system gradually falls off, letting the Gundam use its full strength in battle. Three, weapons for it are found over the course of time, causing the machine to change from having a beam rifle that melts after one shot and antiquated maces to powerful beam sabers and a much more reliable beam cannon. And lastly, the revelation about the power of the Moonlight Butterfly and the Turn A's nanomachines.

* In Literature/TheZombieKnight, The various weapons that [[ExtraOreDinary Hector]] summons up. They could be considered to be more of a representation of his increasing skills and powers as he gains the ability to more precisely summon metal and soul-strengthen it.
* The SpeculativeFiction novel ''Literature/ThePracticeEffect'' has a world where all tools follow this trope. The hero is from "the real world" and figures out that already well-made items from his world have a huge headstart.
** Very unusually for this trope, ''devolution'' is in full effect; any man-made object is slowly shifting back into its near useless "ground state" while it remains unused. For the hero who arrived with goods intended for use on day one this is only a mild inconvenience but craftsmanship and production is at paleolithic levels on this planet.This means if a building remains unoccupied or a tool remains unused they'll both devolve into the worthless poorly secured mud, leaves and sticks they started out as. Well "Practiced" items do tend to become rather specialized; a farmer's pruning shears will over years or centuries become an ultra sharp indefatigable mono-crystal capable of slashing into granite without damage and the hero's robot buddy who never turns off and is thus in constant "use" tends to lose functionality not related to executing its instructions while quickly gaining any abilities that might be helpful in doing its job.

* The ''Weapons of Legacy'' splat-book from ''TabletopGame/DungeonsAndDragons'' 3.5 is based around this. As you level up and take the appropriate Feats, your Legacy Weapon unlocks more and more abilities of scaling power.

* In ''VideoGame/{{Fable III}}'', the first weapons you got are evolving weapons (It's not even a secret) that change depending on what you've done before upgrading the skill (Ranged changed your gun). So every player ends up with a unique weapon by the end of the game.
* Wrath of the Lich King brought the joy of heirloom-type items to ''WorldOfWarcraft''. While the weapons and armor themselves don't grow because of their being used, they still count as Evolving Weapons because they scale to the character's level. This also means they can be recycled and can be used from 1 to 80 before being tossed onto another alt.
** Go back one expansion, to ''The Burning Crusade'', and you find a series of Blacksmith-crafted weapons, each of which can be upgraded twice to a more powerful version. Example: [[http://www.wowhead.com/item=28434 Lunar Crescent]] -> [[http://www.wowhead.com/item=28435 Mooncleaver]] -> [[http://www.wowhead.com/item=28436 Bloodmoon]].
*** Come Cataclysm and Mists of Pandaria, you can reforge your equipment to alter its stats, and upgrade the power of your equipment gotten from heroic dungeons and raids. Further, recent patches now allow you to upgrade your heirlooms to scale to level 85. It's safe to say that ''WorldOfWarcraft'' has gotten fond of this path to giving you legitimate gains in character power between running the gear treadmill each time a new raid releases.
* In ''VideoGame/FinalFantasyX'', the sword Wakka gives to Tidus upgrades automatically when the party visits the Farplane, and Wakka is seen talking to the sword's former owner.
** Also, all of the Ultimate weapons in ''VideoGame/FinalFantasyX'' are upgraded twice, once by finding a relatively easy key item to find, and again by finding a very difficult to obtain key item. They upgrade from Useless weapons which completely stop experience gain, to swords with an ability which also stops experience gain, finally to a weapon which breaks damage limit for both the character ''and'' Yuna's associated Aeon (summon) for them for no particular reason, increases experience gain and has several other abilities depending on the character (One MP cost for Lulu, Counterattack for Tidus etc.) In addition, the final form of each ultimate weapon has a hidden ability, which increases the attack power of the wielding character depending on a certain condition (it depends on the character). And just because all of that wasn't enough, they ignore the enemy's defense stat.
** The Atma Weapon/Ultima Weapon sword in ''VideoGame/FinalFantasyVI'' has an attack power that is a function of the HitPoints of the character wielding it. As they get stronger, so does the sword.
** Vincent's Death Penalty gun in ''VideoGame/FinalFantasyVII'' does more damage with each enemy it kills. Kill about 65 thousand or so, and it'll [[GoodBadBug glitch out and kill anything in one hit]].
** Conversely, the Tonberry's Knife/Grudge attacks in the Final Fantasy series have the ''enemy'' attack get stronger with each kill your characters make.
** The Sequencer in ''VideoGame/FinalFantasyTacticsA2'' gets more powerful each time you get an Opportunity command.
* The Oni weapons in each ''VideoGame/{{Onimusha}}'' game, along with your armor and gauntlet, can be upgraded by absorbing enemy souls. There are three levels of evolution before they MAX out. The weapons, already [[ElaborateEqualsEffective covered in bling]], get increasingly spiky and ornate with each evolution.
* Pins that Neku uses in ''VideoGame/TheWorldEndsWithYou'' will sometimes evolve if you kill enough Noise, or have on him while the DS is off or in mingle mode. [[GuideDangIt You're never informed which needs which]].
* In both ''VideoGame/DarkCloud'' and ''VideoGame/DarkChronicle'', weapons are leveled up by killing monsters with them. Many weapons can also literally evolve if you got their stats high enough.
* The Muramasa in some ''Franchise/{{Castlevania}}'' games will gain attack power as you kill enemies. Something about the sword being cursed and having to drink blood.
** In ''VideoGame/CastlevaniaSymphonyOfTheNight'', the Muramasa puts Alucard in permanent "Dark Metamorphosis" mode; meaning that he recovers health by touching the blood of enemies. The more blood he absorbs, the stronger the sword gets. As such, killing a skeleton won't do anything, but killing a merman will.
* It occurs before the timeline of the games, but ''Soul Edge'' from the ''VideoGame/SoulCalibur'' series of games began as a normal sword, and eventually gained its demonic nature by being bathed in the blood of countless victims.
* The Fell Arms in the ''Franchise/TalesSeries'' are recurring weapons that gain attack power for every enemy their wielder defeats and are by far the strongest weapons available once they're at maximum power (And usually well before that, too).
** In the PSX version of ''VideoGame/TalesOfDestiny'', some of the characters have [[EmpathicWeapon Swordians]], special swords with personalities that can talk. They gain EXP along with their owner, and can level up to get stronger and learn new spells for their owners to use. While all the Swordian Masters of the party have other weapons that they can use, the spells and evolution of the Swordians tends to make them the weapon of choice.
** The Sorcerer's Ring is this in ''VideoGame/TalesOfVesperia''. Over the course of the game higher levels of aer(read magic) will make it shift and become stronger. The plot only requires it to get to level three but to complete the Fell Arms sidequest it has to get to level five.
* Every weapon used in the ''Franchise/RatchetAndClank'' series from ''[[VideoGame/RatchetAndClankGoingCommando Going Commando]]'' on, and in the [[NewGamePlus Challenge Mode]] of the first game, if you've collected enough Gold Bolts.
* ''VideoGame/RetroMud'' has the Fellblade, which is essentially this.
* Weapons in ''[[VideoGame/FrontMission GunHazard]]'' work like this. So do the verniers. And the armor plates. ''And'' the Wanzers themselves (Wanzers and armor actually gain EXP by being hit).
* Weapons in ''VideoGame/CaveStory'' can be leveled up by killing enemies, indirectly. The enemies drop little triangles which can be collected to level up your weapons. On the other hand, getting injured can de-level the weapon you're using. It's inverted for [[LethalJokeItem one powerful end-game weapon which gets weaker when leveled up]], so you have to avoid collecting energy triangles while wielding that weapon. Considering you've now got half a game of [[DamnYouMuscleMemory muscle memory]] telling you to grab the triangles, that's not so easy.
** Averted with another end-game weapon, as you don't have to level it up. It's always at the max power of the Polar Star (the gun you get at the beginning of the game) no matter what you do, but you CAN hold the shoot button and level it up to max (it doesn't level up like any of the other guns, surprisingly) for a supremely powerful laser burst.... Not that you'd need it.
* Fusion and Lumina from ''VideoGame/BraveFencerMusashi''. Each of them gradually gains strength whenever Musashi uses them to attack, and this is separate from his own strength stat. Fusion is also of the second type, as noted below.
* Psyphers in ''VideoGame/OdinSphere'' gain strength by absorbing Phozons, small bits of life force released whenever a living thing dies.
* The Solar Gun Lenses in ''VideoGame/{{Boktai}}: The Sun Is In Your Hand'' inexplicably gain levels up to III by killing things with them equipped.
* The eponymous ''VideoGame/{{Daikatana}}'' gains levels if you use it and becomes deadlier and faster. However your character doesn't gain any experience points this way and does not get to raise his stats.
* [[RaidouKuzunohaVsTheSoullessArmy Raidou]] [[RaidouKuzunohaVsKingAbaddon Kuzunoha]] can visit [[LargeHam affable]] [[MadScientist Dr. Victor]] to reforge his swords: in the first game, he will fuse a demon into the sword, granting it powerups based on the demon's level and abilities, and in the second, a special crystal will be fused into the sword, changing its attributes depending on the used crystal.
* The Sealed J-Sword in ''VideoGame/PhantasyStarOnline''. Normally a semi-decent weapon that inflicts serious status ailments on you, with enough kills with it equipped, and it will evolve into one of the most powerful weapons in the game.
* Dak'kon's zerth blade from ''VideoGame/PlanescapeTorment'', which levels up at the same time he does, being a weapon made of karach, a material of pure chaos that mirrors the mind of its owner. It's referred to in dialogue as something that could become powerful enough to destroy the multiverse itself if fueled by enough will and determination, and while you never see it do anything quite that impressive, it can end up a pretty neat weapon if Dak'kon is in your party right up until the end game. It also can become weaker if you deliberately plunge Dak'kon into doubt and emotional disarray, or become even more powerful by strengthening his belief in the Unbroken Circle, the philosophy he follows.
** Ingress' teeth can also evolve if you ask them nicely, eventually becoming magical of their own volition and adding weapon enchantments.
* Rayne's Carpatian Dragons in ''VideoGame/BloodRayne2'' ''are'' of vampiric nature, and level up through use, to an extent. Simply firing them improves their power and blood capacity, and they also acquire more powerful modes after defeating powerful vampires/dhampirs, even if they aren't used through the entire battle.
* The Chicken Knife in ''VideoGame/FinalFantasyV'' gains an attack point for every time the party has fled a battle. It can easily become the strongest weapon in the game.
** The same game contains an inversion in the Brave Blade, which ''decreases'' in power every time the party flees a battle, essentially making it a devolving weapon.
* A borderline example, but the "Dream Sword" weapon in 'VideoGame/KingdomHeartsI'' (which can only be obtained outside the "Station" via Game Shark) has an attack power relative to Sora's level divided by 10. If Sora is at level 10 or 20, the Dream Sword's ATK is 1 or 2. But if Sora is at level 100, the swords has an ATK of 10, making it the most powerful weapon in the entire game.
* In ''VideoGame/ChronoTrigger'', one of the main characters, Frog, seeks to obtain the sword called the Masamune, prophesized to defeat the villainous Magus. Eventually, you get the weapon and proceed to fight Magus, only to find out his defeat did not save the world by any means, his castle was a DiscOneFinalDungeon and there is still half the game to go. Shortly afterwards, the legendary Masamune is overshadowed by generic weapons from shops. It would be a sad fate for a supposed ultimate weapon... but towards the finale, Frog gets a quest to "[[TimeToUnlockMoreTruePotential unlock its true form]]", which -is- the InfinityPlusOneSword for him. Ironically, due to the sword's plot importance, Frog is the only character who doesn't retain his best weapon in NewGamePlus.
** Ayla's attack also evolves as she gets stronger. As she is an [[BareFistedMonk unarmed fist fighter]], some form of CharlesAtlasSuperpower scaling is expected, but she goes beyond that: as she gains levels, her regular fist is eventually renamed "Bronze/Iron/Steel Fist" on the equipment screen, and each new type gives a new effect.
* In the ''VideoGame/BraveStory'' video game, the main character's [[CoolSword Traveler's Sword]] evolves and takes on new forms whenever he collects certain magical gems (after passing a test of strength and character).
* Items from Franchise/{{Disgaea}} are a borderline case. They can level up and improve, but only if the player ventures into Item World and subdues the inhabitants inside.
* ''VideoGame/TheLordOfTheRingsOnline'' introduced Legacy Weapons with the Mines of Moria expansion. Legacy weapons gain XP and level-up independently from their wielder, with some quests even granting Weapon XP as a specific reward. Each level-up grants points to spend on customising various benefits of the weapon, which can also be enhanced by adding special upgrade-items to it. At intervals of several levels, the weapon must be Reforged by a specialised NPC before it can continue to advance. Reforging allows further customisation of the weapon's abilities, increases its base power level, and allows the player to give it a unique name.
* ''VideoGame/MagicKnightRayearth'' showcases this trope in its first season, in the form of the three main characters' Escudo weapons.
* The ''Dawnguard'' expansion for ''VideoGame/TheElderScrollsVSkyrim'' adds the Dawnguard Rune Axe, which inflicts bonus damage proportional to the number of undead it has been used to kill since the last sunrise.
** ''Skyrim'' also has the Ebony Blade, which increases in power as you kill allies with it.
* Enemies in ''VideoGame/VagrantStory'' have specific types and affinites, and weapons and armor become more effective based on the types of enemies they're used against. Kill lots of dragons with a spear, and it'll gain dragon points that make it more effective against dragons in general. Kill lots of fire-type enemies and it'll become a water type weapon.
* In ''VideoGame/{{Drakengard}}'' and its sequel, all weapons can level up. As they level up, all their stats go up (except weight) but their appearance changes and they also explain the history of the weapon with each level up. They can only be leveled up four times and visual change only occurs in the first Drakengard.
** At least one weapon has good reason for this. Its blade is encased in stone, and as you kill enemies with it, it levels up like everything else. It does this by breaking some of the stone off.
* ''VideoGame/{{Diablo}} II: Lord of Destruction'' introduced several magic item properties that scale by character level, including bonuses to armor value, damage, and accuracy. Unfortunately, they're rarely worth keeping for very long, as something better will usually [[RandomlyDrops drop]].
* ''VideoGame/{{Dragonfable}}'' has the Doom Knight equipment set, [[BribingYourWayToVictory only available through a cash upgrade]], which increases in power every ten levels. At level 60 (the level cap at the time of this edit), the [[DoomyDoomsOfDoom Necrotic Sword of Doom]] is the best Darkness-based weapon in the game - and its special attack deals [[ThereIsNoKillLikeOverkill 12 hits of regular attack damage]], which is easily enough to reduce anything with a weakness to it to a pile of smoking ash.
* ''VideoGame/SuperRobotWarsAdvance'' has the protagonists' machines, ''VideoGame/SuperRobotWarsZ'' has the Gunleon, and in ''VideoGame/SuperRobotWarsL'', the Rushbird gains new attacks and abilities as the game progresses.
* Varric from ''VideoGame/DragonAgeII'' can never equip any other weapon than his beloved AutomaticCrossbow [[ICallItVera Bianca]]. Fortunately it levels up with him so it never becomes obsolete. Even better, any rune attached to Bianca also becomes stronger.
** [[{{DLC}} Various downloads]] also feature "improve with level up" items, with 1 dedicated accessory per companion, and a few that can be given to anyone capable of equipping them, including weapons.
* In the third VideoGame/{{Resistance}} game, all the weapons upgrade with use. Said game is also made by the creators of the ''Franchise/RatchetAndClank'' series.
* In ''VideoGame/HeroesOfMightAndMagic'' ''VI'', playing online allows you to find Dynasty Weapons in the campaigns. If a hero wields said weapons, they gain experience along with the hero. Each weapon has several different abilities that can be unlocked with exponentially increasing amounts of experience, ranging from passive stat bonuses to enemy debuffs/ally buffs.
* In ''[[VideoGame/FireEmblemJugdral Fire Emblem: Genealogy of the Holy War]]'', weapons with at least 50 kills gain the critical ability, with the chance of getting a critical increasing with each additional kill up to 100.
* The Protoss Vindicator (also known as the Soul Hunter) in the ''{{Starcraft}} II'' beta had a weapon that leveled up as it killed enemies. It was cut due to a number of difficulties -- it was hard to indicate when (and why) Vindicators leveled up, it was too random in large-scale battles, and it was basically impossible to balance; its reliance on kills made it much more powerful against [[ZergRush the Zerg]].
* The Ivandis flail and blisterwood weapons on ''VideoGame/RuneScape'' , designed to kill vampires, gain stat boosts and max damage bonuses, respectively, as more vampires are defeated and cremated.
* The Yearbook Club Camera from ''VideoGame/KingdomOfLoathing''. It's an accesory that does nothing at first, but gets stronger with each assigned monster defeated and the picture returned to the Yearbook Club the next day.
* The titular weapon of ''VideoGame/{{Xenoblade}}'', the [[LaserBlade Monado]] is all about this. As its wielder gets stronger (I.E. leveling up), the sword itself does as well. Moreover, in addition to the not-so-useless trait of allowing its wielder to [[CombatClairvoyance see into the future]], it gains a number of abilities such as shielding, granting speed boosts, and purging auras over the course of the story.
* ''Videogame/PathOfExile'' brings a twist to this trope. The weapons and armor stay the same over time (unless upgraded by other means, like the blacksmith's whetstone for weapons), but the ''[[SocketedEquipment gems]]'' inserted in their sockets level up after a sufficient number of monsters is killed while the weapons and armor are equipped (not just carried in the inventory, though), improving the skills granted by those gems.
** The 2.3 ''Prophecy'' update adds the Fated Unique mechanic, allowing players to upgrade certain unique items and grant them new powers. For example, if a character has drawn the King's Path prophecy and kills Kaom while wearing the Kaom's Sign unique ring, it upgrades to Kaom's Way and grants extra life regeneration.
* ''VideoGame/StarTrekOnline''
** Mark Infinity equipment improves in effectiveness as the PlayerCharacter levels up.
** The ''Delta Rising'' expansion introduced Tier 5-Upgraded and Tier 6 starships, which have a Starship Mastery feature which enables the PlayerCharacter to grind skill points to unlock stat boosts on that ship, as well as [[SkillScoresAndPerks a perk]] in T6 ships which is usable on any ship.
* The ''White March'' expansion to ''VideoGame/PillarsOfEternity'' added Soulbound equipment (almost all weapons), that can be bound to a character and then is upgraded when specific requirements are fulfilled (most of them allowing for simple 'kill enough foes'/'trigger the special ability of the weapon enough times' as a fallback from more specific requirements). Some do vary the formula -- one sword is cursed, automatically binds to whoever picks it up and can't be dropped until you upgrade it to its highest tier (which you do by interacting with various places throughout the game), while one dagger actually gets ''worse'' as it is levelled up (until the final tier, when it suddenly turns into the best dagger in the game).

!!Examples of weapons with temporary upgrades/changes

[[AC:{{Anime}} and {{Manga}}]]
* In ''Manga/ArataKangatari'', Hinohara's Hayagami, Tsukuyo, gains the ability to transform from its initial dagger form to a longsword. It reverts back to the dagger form when it's not in active use.

* [[Literature/TheElricSaga Elric's]] sword, Stormbringer, will get stronger after killing some poor sap and eating his soul.
** Stormbringer not only gains strength from feeding on someone's soul, but makes Elric stronger as well (remember he's an albino who previously needed drugs to maintain his strength). Elric's dependence on Stormbringer is an addiction - he tries to kick the habit several times but always finds himself drawn back, until ultimately it destroys him. (However, the comic series ''Creator/MichaelMoorcock's Multiverse'' gives him a second chance at salvation.)
* In the light novel and manhua ''[[Literature/HalfPrince 1/2 Prince]]'', the prince starts the series with a black dao that can level up with the user.

* The fourth edition of ''TabletopGame/DungeonsAndDragons'' features some magical items -- most notably rings -- with abilities that only become available once their would-be user has reached a 'milestone', i.e. has made it through two encounters without taking an extended rest in between. Similarly, the accessible powers of fourth edition artifacts as a form of EmpathicWeapon wax and wane with how much in tune the current owner's actions are with the artifact's own goals. -- Perhaps less directly applicable to this trope, the game also features a limit on how many magic item daily abilities a ''character'' can use per day, even if they were to carry a veritable grab-bag of such items with them. Each milestone reached extends this limit by one for the current day, thus potentially 'unlocking' item powers that the character could not have used otherwise.

* In ''The Shivering Isles'', the expansion pack to ''VideoGame/TheElderScrollsIVOblivion'', there Dawnfang/Duskfang sword transforms between the two forms every dawn and dusk - but if you've killed 12 enemies with it during the preceeding period, it instead becomes the 'Dawnfang Superior' or 'Duskfang Superior', with additional, life-stealing powers.
* The sword "Fusion" in ''VideoGame/BraveFencerMusashi'' has the power to "assimilate" enemies, thereby [[PowerCopying gaining their abilities]]. It can only hold one ability at a time; gaining a new one overrides the old one. It is also of the first type, as noted above.
* In the [=PS2=] game ''VideoGame/{{Shinobi}}'', enemies you kill with Akujiki take a few seconds to actually fall over dead. During this time, Akujiki glows with power and does more damage, allowing to kill more enemies in rapid succession to further extend the time before they die. It is possible to one-hit kill every boss in the game if you kill their [[FlunkyBoss minions]] fast enough first.
* In the ''VideoGame/MegaManBattleNetwork'' games, there are two BattleChips (a.k.a. weapons programs useable once per battle per chip) that you can gain, both swords, called the Custom Sword (CustSwrd) and the Muramasa, respectively, that gain power due to a special condition -- in the Custom Sword's case, its power is determined by the 'custom gauge' at the top of the screen (it can get to around 200 maximum, but when the bar maxes out the power immediately drops to 0), but in the Muramasa's case, it will hit the two panels in front of Mega Man for an amount of damage equal to the HP HE'S LOST. Capped at 999, sure, but 999 in ONE ATTACK (when most Mooks will have phenomonally less, and most bosses hit will lose around or over half their HP) is kind of a big deal.
** The manga explains this as the weapon feeding off of its user's pain and suffering, which its current user in the manga goes out and gets plenty of -- though one of the more Genre-Savvy members of the Quirky Miniboss Squad (who were all not-so-coincidentally all bosses from the same game) decides to render it all moot by shooting the man in the hands with a Frickin Laser Beam so that he can't hold the Muramasa (what good is an Infinity Plus One Sword if you can't actually SWING it, after all).
* In ''VideoGame/HalfLife2'' and ''Episode 1'', there is a point where the Gravity Gun gets a temporary upgrade and has the ability to lift much larger objects and pick up the combine soldiers to fling them as projectile weapons! This upgrade happens in the end of ''Half-Life 2'' and in the beginning of episode 1 where it's only for one area and then it downgrades.
* In ''VideoGame/TeamFortress2'', the Demoman has a sword called the Eyelander which he can use to decapitate enemies. Each head gives him extra health and boosts his speed at least, until he dies.
** The Engineer has his Sentry Gun, which starts with a simple turret. Upon leveling up via metal, it can "level up" to a double-barreled minigun, and again to add a 4-rocket rocket launcher.
* Enserric, the vampiric sword in ''VideoGame/{{Neverwinter Nights}}'' expansion Hordes of the Underdark, gains the ability to drain its wielder's health to give itself a temporary boost.
* The Marker in ''VideoGame/{{Qix}}++'' can be upgraded in four features using points earned in the stages. Its appearance changes the more upgrades you get. Unfortunately, it's only good in the section you're playing. Start a new section, and you're back to the crappy Marker you started with.
* In ''VideoGame/AdventureQuest'', weapons and armor gain power the more you level up; weapons increase in base and random damage, and armor in defense and hits of attack.
* DoubleSubverted with the Keyblade form the ''VideoGame/KingdomHearts'' series, while the weapon doesn't grow itself, you can attach various keychains (or gears in days) to it in order to alter its form and properties such as strength and magic bonuses in (almost) all the games, extra abilities in II, days and Birth by Sleep, attack patterns in Days and Clock gauges in Re:coded. The double subversion in this example, is that the keychains used to modify the keyblade are essentially memories of people and locations used to modify the [[EmpathicWeapon keyblade's form]], the keyblade itself doesn't change, only its form.
** The individual Keyblades themselves will level up in ''Re:Coded''.
** Riku is a straight-up example. Because of his Keyblade choosing Sora over him when he chose to open himself to darkness, he's had to compensate with a dark sword he manifested, called the Soul Eater, an EvilWeapon with the blade shaped like a devil wing. However, towards the end of Kingdom Hearts II, it has evolved into a proper Keyblade called Way to the Dawn, straightening and lengthening the wing plus adding angel wings to the design. The next chronological entry, however, shows that he is still able to summon the Soul Eater form, though no longer uses it, signifying his turn from the dark for good.
* ''VideoGame/LegacyOfKain: Soul Reaver 2'' has the named Soul Reaver - remnants of a powerful magic sword, fused with the protagonist. It becomes stronger when Raziel hits with it. It becomes ''much'' stronger when it consumes the soul of a killed enemy. It starts to eat the wielder's life when it becomes overpowered. And it slowly returns to its normal state when combat is over.
*** In ''Legacy of Kain'', it used 1 mana rune per swing, but basically 1-shotted whatever it hit and had a pretty wide hit box so you could wipe out several enemies per swing (without mana it was only as strong as the starting iron sword). Was 2hded and prevented spellcasting. In Soul reaver 1, it was simply 3 times as strong as claw attacks and could be used to finish enemies and maintained your life bar in the physical realm, but could only be manifested at full health or in always in the spectral realm. In Defiance it was just an attack and didn't evolve per say (though you could unlock other elements/abilities by collecting crest pieces (Blood Reaver) or elemental spirits (Soul Reaver)).
* Skill Cracking in ''VideoGame/DevilSurvivor'' works like this: you hunt down a demon who holds the skill you want with a specific character. If said demon successfully dies at the hands of that character, you wil gain the option of adding that skill to your set. Later, certain game mechanics allow you to teach cracked skills to your demons.
* The player's default weapon in ''VideoGame/BinaryDomain'' is an assault rifle. In early stages, it performs about as well as a standard assault rifle should against MechaMooks. By the endgame, a fully upgraded assault rifle is practically a light machinegun tearing through hordes of mooks.
* The new Pulsefire Ezreal skin in ''VideoGame/LeagueOfLegends''.
* Honedge from ''VideoGame/PokemonXAndY''. Being a Pokemon in itself, it gains stronger stats and learns new attacks when leveling up. Taken literally when it evolves into Doublade.
* In ''VideoGame/TowerOfGuns'', getting blue orbs and crystals fills your weapon level bar up to 5 times, giving it increased stats, but taking damage drains a chunk of the bar.

* Torg's sword, Chaz, from ''Webcomic/SluggyFreelance'' will become powerful and able to talk once it has come into contact with the blood of an "innocent" person.