Penultimate Weapon

So you just found out that The Dragon is the hero's father and got the Final Ultimate Maximum Infinity Sword, now you just got to The Very Definitely Final Dungeon and... wait, what? Why is this random sword you found better than the supposed "ultimate weapon"?

The reality is, just because everybody you've ever met hailed your shiny weapon as the mightiest in all the world doesn't always mean that they're right. And don't get too attached to that new sword you found - expect to find a weapon that outclasses that in, or for clearing, the Bonus Dungeon.

The weapon version of Overrated and Underleveled. Quite frequently overlaps with Sword of Plot Advancement. May be replaced by an Infinity Minus One Sword.

Action Adventure

 * In The Legend of Zelda titles, the Master Sword is frequently outclassed by other weapons and/or improved versions of itself.
 * Specifically, in The Legend of Zelda: A Link to the Past. The Master Sword can be upgraded twice, making the original Master Sword your Infinity Minus Two Sword. Which is funny, considering there are only 4 swords in that game. Infinity Minus Three would be your starting weapon.
 * It also happens in a linked Oracles game, Wind Waker, and Twilight Princess.
 * Also in Ocarina of Time the Master Sword is overpassed in range and damage produced by the Biggoron Sword. Its obtained in an optional quest and only has the disadvantage of needing to be wielded with the two hands making it impossible to use the shield. Still, the weapon used to finish the Big Bad is the Master Sword. The Biggoron Sword will work for most of the fight, but only the Master Sword can strike the finishing blow.
 * Alucard's Sword in Castlevania: Symphony of the Night. When you get it back, you may or may not have found a better sword (or a certain rod and shield combination). The real ultimate weapon is the rarely dropped Crissaegrim, which has lower attack power than the Alucard Sword but does more damage per swing anyway due to Death of a Thousand Cuts.
 * To make the Crissaegrim even more game-breaking, it's possible for two of them to be dropped. Since they're one-handed, so you can dual wield them.
 * It's subverted in Portrait of Ruin where the Vampire Killer is hyped up to be a powerful (if not the most powerful) weapon the hero could have...but he has it already, and due to a seal on its power, it's the weakest weapon in the game. Only by beating a Bonus Boss do you unlock its true power, and due to the fact that most enemies in the game are weak to both holy and whip-type damage, it really does outpower and outrange damn near every weapon you can get.

First Person Shooter

 * This can happen in Borderlands with Atlas guns. They're supposedly the best you can get, but due to the random weapon generation system, its easily possible to get much better guns from the piles of skag vomit you see everywhere. Or in the same damn chest.

Driving Game

 * The BMW M3 in Need for Speed Most Wanted definitely counts. You can get much better results from a fully tuned Vauxhall Monaro by the time you recover it.
 * I see your Vauxhall and raise you the Fiat Punto and Cobalt SS, which are tied for 3rd fastest cars in the game after the Carrera GT and Lotus Elise given full junkman parts. That Cobalt just keeps accelerating.
 * Honestly, one of the coolest parts of the game is the fact that you can take a Golf GTI and make it faster then the police spawning engine at level 5 is sweet
 * Only in single player. In multiplayer, its stats are so utterly sad that the game takes mercy on you and detunes the other cars. Unfortunately, it does so by lowering their handling while buffing the handling of the M3... which neatly solves its biggest problem and transfers it to everyone else. If there is so much as 1 M3 in a multiplayer match, you have to roll out your own because any other car will now drive on ice.
 * The boss cars in Need for Speed Pro Street are nearly useless. For beating the Grip King, you get an M3. Yay. You're probably driving at least a 911 Turbo if not a Pagani Zonda at that point. The Speed King's GTO is one of the slowest cars in the game, not to mention its complete lack of downforce which prevents you from even going fast at all without randomly flipping over and exploding into pieces. And even discounting the many glitches in drag that allow you to build a 3.5 second Toyota Supra, the Mustang you get from the Drag King is probably worse than any other RWD car you can buy except the Aston Martin. And the ultimate end boss car is a Lancer Evo. The only sensible boss car is the Drift King's RX 7.
 * Gran Turismo 3 has the late game professional events, notably Like The Wind. For completing this event, you get the Mazda 787B. Yay, yippie woop-de-do, a LeMans Prototype as my reward. Too bad that this is an S-License event--and endurance races are available once you have an IA License. Said endurance races reward you with a far superior Formula One car, that is, if you have the luck to earn it thanks to the crappy in-game prize system.

Fighting Game

 * Expect to do a lot of grinding if you want the Ultimate Weapon for your favorite character in Dissidia Final Fantasy (and yes, it's different for all 22 of them)... but turns out that the actual Ultima Weapon is a huge case of Guide Dang It requiring special passwords, materials, and Item Crafting recipes to create. And even then, it is a Situational Sword which is only at its best when you have max HP.
 * In the Soul Calibur games, characters who get Soul Edge, supposedly the most awesome sword ever (except to people who know about the Soul Calibur), have a Legendary weapon that trumps Soul Edge.
 * This varies, however, depending on the particular stats and effects of each characters particular Soul Edge and Legendary Weapon.

MMORPGs

 * Strangely, the Kingdom of Loathing has three. At about level five, you get to smith your class's "Epic Weapon", which has a high power, gives a large stat boost and (for some classes) doubles the duration of buffs that they cast. Soon after that, you get to turn it into the "Legendary Epic Weapon", which has even more power, a larger stat boost and triples buff duration. During the final part of the Nemesis Quest, the LEW upgrades to the Ultimate Legendary Epic Weapon when fighting your nemesis's One Winged Angel form. The ULEW all have the highest possible weapon power (coupled with a lower-than-normal requirement to equip), large stat boosts, all the benefits of the older forms and give access to a special combat move when equipped - and for buffing classes, the buff duration is quadrupled.
 * Then, when it all comes down to it, it doesn't match up to half the weapons you find later on.
 * Any ultimate weapon in World of Warcraft that's from an earlier expansion pack (or, goodness forbid, from the unexpanded game). Thunderfury, for example.
 * Really any gear from previous content. Within the same expansions the best gear from one raid tier (with some exceptions) lies between the low and medium grades of the next tier. When new expansions come out, the very best and hard to get stuff from previous one is eclipsed by lowly quest rewards before long. More, Cataclysm has made it so that it's finally true what people have been incorrectly (exaggeratedly) claiming about the previous expansions: the lowest new items are immediately a match (almost) for the best old ones. It's probably because getting really good stuff was made much easier in the previous expansion.
 * Happens a lot in Maple Story. Considering the max level being lv 200 and the highest level equipment available overseas in the Korean version being 140, there will always be much room for game designers to add better, and stronger equipment in the future.
 * Not only do new equipment could come out, new, more dependable methods of improving existing equipment have come out often over time. Any weapon considered good before new items used to enhance equipment come out, would be less good because it becomes easier (though usually either more risky or costly) to make something better then before.

Role Playing Game

 * The Excalibur from Final Fantasy I is second in power to the Masamune, which is found in the final dungeon. Odds are good, though, that you'll let the Fighter/Knight keep using Excalibur - it can only be used by Fighters/Knights, while the Masamune can be used by anyone, so you'll probably give it to your Thief/Ninja or Red Mage/Red Wizard.
 * In the Dawn of Souls release for the Game Boy Advance, you obtain the Ragnarok after defeating Shinyru on the 20th level of Lifespring Grotto. However, after you complete all 40 levels of Whisperwind Cove and kill the weaker Death Gaze and obtain the less powerful Lightbringer, you can find a treasure chest that contains the Ultima Weapon, a sword that does damage based on the wielder's HP, making it twice as strong as the Ragnarok.
 * The 20th Anniversary Edition tops this with the Barbarian Sword, which has 134 attack, where the Ultima Weapon could only go up to 100.
 * While you spend at least one-third of Final Fantasy II chasing after the Ultima spell, it really isn't that great if the player doesn't max out every spell, weapon level and stat; otherwise a Flare or Holy spell does more damage.
 * In Final Fantasy IV, the Legend Sword that Cecil gets upon his Heel Face Turn is quickly outclassed, but can be upgraded to the much better Excalibur near the endgame, once you get some special ore and take it to the Ultimate Blacksmith. Excalibur still turns out to be the Penultimate Weapon though, as following a secret path in The Very Definitely Final Dungeon leads you to the vastly better Ragnarok.
 * Then in the Updated Rerelease, even Ragnarok is one-upped--in the GBA version you get the Lightbringer, and in the DS version you get the Onion Sword.
 * The Twelve Sealed Weapons from Final Fantasy V. Even though four of them are the most powerful weapons of their respective types, they end up being inferior to those gained elsewhere.
 * The Eternal Blade in Tales of Phantasia is outclassed by some Bonus Dungeon weapons. It doesn't stop other Tales games from using it as a proper Infinity Plus One Sword. Tales of Eternia reverses this, as it's the Excalibur that serves as the Penultimate Weapon to the Eternal Blade.
 * Likewise, Lloyd's Material Blade in Tales of Symphonia is outclassed quickly by the Ninja Sword found in the last dungeon (to add insult to to injury, the Final Boss is also weak to it) and two sidequest rewards (the Valkyrie Saber and the Kusanagi). Lloyd's Devil Arm should outclass all of them unless you have been running from most of the fights.
 * Even sadder, the paper fans you can buy in Luin are at least as good as, if not better than, the Material Blade.
 * Funnily enough, the scene where Lloyd gets the Material Blade is accompanied by this quote: "I doubt you have a blade in your possession that can match it." Guess what? You can get one of these sword sets before that point.
 * Well, now, let's be fair to poor Dirk. Lloyd uses two swords at once. Dirk is almost certainly referring to how Lloyd doesn't have a sword that matches the one he's just received from Kratos, thus why he proceeds to give him another one that becomes the other half of the set.
 * The Material Blades also allow you to use the Limit Break, as they are the two component swords of the Eternal Sword. And they just look cool.
 * In Eternia, the Eternal Sword might also still count depending on when you get it. As it was only the ultimate weapon in terms of sheer power, sacrificing other stats for it. Not to mention its Time element weakens it against certain enemies. The game had a few other weapons like it too. The true Infinity Plus One Sword was the Last Fencer. While not as strong in terms of sheer strength, it had no element, and the advantage of raising all stats at once. It also may or may not be named after one of titles Cless gets in Tales Of Phantasia. So um... Take That?
 * Although the Dragon Sword is implied to be the Infinity Plus One Sword of the first Breath of Fire, it is outclassed by not only the Trirang and the Emperor's Sword, but one weapon you can buy from a store, the Flame Sword.
 * The Elder Scrolls III: Morrowind: While Chrysamere is hailed as the best long sword in the game and is a true BFS, it is slightly inferior to the Hammer Of Plot Advancement Sunder, which at no point is described as anything but a tool to achieve the final task (it is a hammer). According to the Guide Dang It, the Infinity Plus One Sword are supposed to be Goldbrand and Eltonbrand, but those are Statistically Speaking even worse than Chrysamere. The true Infinity Plus One Sword is
 * Or
 * The Ultimate Bat in Earthbound is an Infinity Minus Four Weapon; there are actually four more bats in the game with greater offensive power, three of which are discovered in the course of normal gameplay. The Legendary Bat is quite strong, but the super-rare Gutsy Bat is the true Infinity Plus One Sword.
 * Albel Nox's Crimson Scourge from Star Ocean Till the End of Time.
 * At least you can upgrade it to your liking.
 * In Star Ocean 2, Claude's Penultimate weapon is the Eternal Sphere, which stuns enemies with each blow. It's very much out-classed by the Levantine found in the final dungeon, with nearly twice the attack power.
 * That depends on if you have an angel armband equip or not. For almost all the games fights the eternal sphere is the best because all competition is obtained nearly after the main story is finished and every attack you do throws out 12 stars that stun the enemy and do half the damage of your standard attack. Once you equip an angel armband though the eternal sphere loses its edge over better swords because every attack does this regardless of the weapon and you get some rather hefty stat boosts plus all element immunity. Of course this awesome item can only be obtained if you manage to beat one of the hardest bonus bosses in the game.
 * Sword of Vermilion is a repeated offender. The titular sword is not the strongest sword in the game, there is a stronger blade in an obscure dungeon. It's not even a Sword of Plot Advancement, getting it is optional and it can be missed. (Especially by Save Scumming, as getting it requires you let something bad happen to your character.) Also, the game features two items called Ultimate Sword and Ultimate Armor. Neither of them is. And the Dragon Shield, which is heralded as very powerful and requires a little backtracking to get, pales in comparison to a shield you can simply buy in the very next town.
 * In Chrono Trigger Masamune doesn't remain Frog's best weapon for long. (But much later, its upgraded version does.)
 * Ironically, in the rerelease, he gets screwed by the lack of this. Everyone gets a great upgrade to their weapon, making their last weapons obsolete. Frog gets a weapon that is slightly worse than the Masamune. Worse, since the Masamune is a plot item, you lose it {and the upgrade} every new game, though you do get to keep the new item from the Bonus Dungeon, which is probably the point of it. He does get the Champion Badge (an improved Hero's Badge), which needs to be used with... the Masamune. It also halves all his MP costs.
 * Yup, that's exactly the point. His upgrade weapon isn't a new Penultimate Weapon, it's a new Infinity Minus One Sword (the Dinoblade outclasses the Brave Sword, and thus becomes Frog's default weapon for 90% of a New Game Plus).
 * In Skies of Arcadia, the Vorlik Blade is the Infinity Plus One Sword. In the the expanded Gamecube rerelease Legends, however, it plays Penultimate Weapon to a secret sword that can only be claimed through One Hundred Percent Completion.
 * Which is all but worthless except as a Bragging Rights Reward, because the Vorlik can hit the damage cap anyways.
 * The original Ys plays this absolutely and irredeemably straight, forcing you to collect the legendary silver (!) equipment before you enter the final dungeon, then giving you better equipment of each type if you search the right treasure chests in that dungeon. Ultimately, the stuff isn't even necessary for beating the final boss, apart from the previous But Thou Must.
 * Actually, using the better equipment you gain in the final dungeon makes the final bossfight significantly harder.
 * In fact, in many of the games, the final boss can only be damaged with the penultimate sword.
 * In Tactics Ogre, the Penultimate Weapon is the Brynhildr, which drives much of the plot and plays a vital role in the final dungeon. However, it's outclassed by multiple weapons in the PSP remake.
 * In Lufia II the Sky Sword you can find in the Ancient Cave and the Dragon Blade you can buy for an insane amount of money in the casino are stronger than the legendary Dual Blade.