Batman has always understood that his allies on the Justice League have the potential to go from the world's saviors to its gravest threats, and as a result, he has put time and resources into developing technology to use against members of the League should they go bad. These are the kinds of weapons Batman hopes to never have to use, or to only have to use once.

There are many iconic Batman gadgets from throughout the years, but as effective as a simple batarang might be, as useful as a grappling gun is in certain situations, fighting off the superpowered members of the Justice League necessarily requires something a bit more involved. Below are fifteen of the best anti-Justice League weapons Batman has used, which have only appeared once.

15 Anti-Flash Grenades

Speedsters are some of the most dangerous superpowered individuals on Earth, able to easily cover the entire planet in just a few minutes. Flash proved he's faster than Superman in Injustice when Barry Allen was able to find Batman's hidden base after searching every single inch of the planet, a feat which took him roughly an hour. This is after years of Superman trying to track down Batman. Barry did it in an hour. To combat this insane speed, Batman invented grenades that drained the Speed Force from any Speedster caught in the radius of its blast. This was first seen in Dark Crisis on Infinite Earths #5, where Batman, while having lost his memories, uses the gadget on the Flash to prevent him from moving.

14 Batcave Ice Guns

When Batman was attacked by Eobard Thawne during the events of Batman/The Flash: The Button, the Caped Crusader was utterly outmatched. Thawne beat Bruce within an inch of his life; the only reason he survived was that Thawne was killed by Dr. Manhattan after picking up the titular button. After this encounter, it seems Bruce learned that the Batcave is not secure against Speedsters, so he outfitted the cave with enhanced versions of Mr. Freeze's cold gun. Considering one of Flash's biggest nemesis is Captain Cold, there's no doubt this new defensive measure would be effective at least at slowing down any intruders.

13 Anti-Green Lantern Silica Powder

During the events of DC vs Vampires, Hal Jordan was one of the vampire king's best agents, having infiltrated the Justice League and managed to infect several key members, including Wonder Woman. When Batman began to figure out the mystery of the vampires, Green Lantern came to kill Batman. However, Batman was prepared for their encounter. He set off a yellow silica powder bomb, instantly blanketing the Batcave in yellow powder. Green Lantern's weakness is yellow, and as a result, Batman's ingenious tactic immediately dampened the former hero's power, allowing Green Arrow to land a near-fatal hit on him.

12 Kryptonite Dust False Tooth

Also, from DC vs Vampires, when Hal Jordan came to kill Batman he brought several members of the Justice League along with him. While Hawkgirl, Cyborg, and Superman weren't yet infected, Hal knew Batman wouldn't go quietly, and would instead put up a fight, which would only make him look more guilty. When Superman tries to restrain Batman, telling him that he can't win this fight, Batman activates a fake tooth carrying Kryptonite dust, blowing it into Superman's face and immediately disabling him. To be able to use this against Superman, Batman would have that false tooth implanted possibly years before, anticipating the inevitability of conflict with his friend and ally.

11 Anti-Boy Scout

During the events of Batman/Superman Annual #1, Mxyl and Bat-Mite were shown arguming over who would win in a fight, Batman and Superman. The two floated ideas such as Batman turning the sun red to defeat Superman. The most interesting, and most likely, was Batman installing the Anti-Boy Scout protocols in the Fortress of Solitude. In this scenario, when Batman gives the word, anti-Kryptonian defense systems activate and zap Superman with kryptonite electricity in his own home. While this may seem a bit tricky of a maneuver to pull off, a dark version of Robin did almost the exact same thing to Superman.

10 Making Aquaman Hydrophobic

Batman has multiple plans to take down each member of the Justice League, with these plans necessarily based on certain well-known weaknesses of characters such as Martian Manhunter or Superman. However, when a character has no real weakness, the only option is to remove the source of their power. This is exactly what Batman did when he designed a special strain of the Scarecrow's Fear Toxin, one that targets Aquaman. This was seen in the Tower of Babel storyline and while Batman has never actually used this plan against Aquaman, his son Robin did. The toxin was engineered specifically to make Aquaman horrifically hydrophobic, preventing him from going anywhere near water, keeping him at human-level strength, and thus preventing him from being a serious threat.

9 Stealing Green Lantern's Ring

Members of the Green Lantern Corps are some of the most powerful heroes in DC, wielding an absurdly powerful ring that lets them create whatever they can imagine, in addition to giving them dozens of other powers, such as flight and the ability to create physical barriers. Green Lanterns are only as powerful as long as they are wearing their ring, which Batman figured out when he stole Hal Jordan's way back in 2012's Justice League #1. Batman has managed to steal a Green Lantern's ring more than once, not only depriving them of their powers, but granting him access to a level of abilities unparalleled even by his most significant inventions. While there are other ways to combat a Green Lantern, stealing their ring is certainly the most efficient.

8 Defeating Superman By Whistling

During the events of Batman #42, the majority of humanity had been taken over by Poison Ivy. With her controlling everyone on the planet, except Batman and Catwoman. In this story, Batman was able to take down Superman in a way that wouldn't normally work, due to the fact that he was vulnerable as a result of Ivy's control of his mind. In one of his most rousing moments, Batman disarmed Superman with a simple whistle. Due to Superman's hyper hearing, the sudden high-pitched noise knocked the Man of Steel out cold. It's important to note Batman does state this only worked because Superman wasn't in his right mind, but it's still incredibly impressive.

7 Kryptonian Strength Gloves

Batman Beyond #1 depicted an older, alternate version of Batman wielding a gauntlet that seemingly provided him with Kryptonian-level strength. The biggest issue for Batman in any fight against superhuman opponents is their absurd strength level compared to even the strongest baseline human. It is understandably difficult, to say the least, to fist-fight a peron who can level entire skyscrapers with a flick of their wrist. With the use of this gauntlet, Batman was able to harness power on par with Superman, allowing him to do things such as easily destroy a moving crate full of dangerous weapons.

6 Hypnosis

When Lobo is hired by the Joker to kill Batman in Batman/Lobo, Batman is forced to throw everything he has at the Main Man to try and stop him. Due to Lobo's regeneration abilities, as well as his strength, he tears through everything Batman puts in front of him, including Tim Drake and Dick Grayson. Despite all of this, Batman does manage to eventually stop the deranged bounty hunter in an unexpected way, by hypnotizing him. Using a reflective mirror and some gas, which increases susceptibility, Batman is able to successfully reprogram Lobo and order him to leave the planet.

5 The DCeased Protocols

When the DC universe was struck by a zombie virus, billions of people died instantly, including many of the world's greatest heroes. Batman was among the first wave of deaths, but prior to his death, he left something for Damian Wayne, delivered by Alfred in DCeased #4. It was a briefcase containing a new Batsuit, fitted to Damian's build, as well as items with a symbol of each member of the Justice League on them. Considering later in the finale it's shown the Superman one had Kryptonite in it, it's likely each one has a way to take down the corresponding hero. Considering how dangerous zombie Superman was in DCeased, these plans could've been absolutely invaluable but Damian never ended up using any of the others.

4 The Justice Buster

When the Justice League became Jokerized during the events of Batman: Endgame, the twisted versions of the heroes unleashed hell on Gotham City, immediately attacking Batman with everything they had. Batman was forced to turn to one of his most notable contingency plans for just such an occasion. Bringing out a suit of armor known as the Justice Buster, a machine that was specifically designed to keep up with every single member of the Justice League, Batman fought to contain the Jokerized versions of his friends by using the suit's tech, specifically designed to be fast enough to catch The Flash and strong enough to fight Wonder Woman.

3 Failsafe

Batman has contingencies not only for all the other members of the Justice League but also for himself. If Batman ever went evil or started killing people, Failsafe would be activated. Failsafe was made to stop Batman if he ever crossed the line, first appearing in Batman #125. Its protocols included contingencies for any possible situation where the Justice League joined Batman in killing people. Failsafe was able to easily take on the entire Justice League, and most shockingly, he did it in a variety of ways. While the machine used Kryptonite in its fight with Superman, it ultimately took Superman down using pressure points, showing he had multiple ways to deal with whoever his target was.

2 Tower of Babel Protocols

The greatest defeat the Justice League ever suffered was at the hands of Batman, in a way. After Batman's contingency plans were stolen by Ra's al Ghul, he modified Batman's original non-lethal plans to make them lethal. With only slight adjustments, Ra's almost destroyed the Justice League with little issue, as seen in the iconic Tower of Babel story arc. The only reason he didn't succeed was his inability to stop Batman from interfering to save his allies, since these were originally Batman's plans, he knew what Ra's would do and was able to help plan a counter-attack.

1 The Final Batsuit

By far the most powerful single-use Batsuit in the character's history, the Final Batsuit was created for Batman by The World Forger, a being who literally created entire worlds, as seen in Justice League #24. Batman donned the suit to try and defeat the Justice League, seemingly seeking to make them submit to the World Forger's plan to change reality. In actuality, Batman acted like he was fighting the League, but in fact he manipulating things to help Superman escape imprisonment by World Forger. Fighting the League and manipulating events was made easy, considering the Final Batsuit has absurdly impressive abilities: it was nearly indestructible, granted incredible physical strength, and gave Batman the ability of mind control, providing Batman with power unlike anything he's ever had before or since.