DC Comics is a brand grounded in reality and high fantasy at the same time. The latter helps produce some of the most fantastical weapons and items conjured from the imaginations of the writers. Unfortunately, this means certain weapons are simply too over-the-top to be taken seriously outside of the comic book pages.
If certain weapons from DC's arsenal ever made their way into the real world, they wouldn't do a lot of good. Some are so impractical that they wouldn't operate as intended, while others might end up destroying the very fabric of the universe, itself. Either way, these are weapons that sound good on paper, but do nothing in a real scenario.
Wonder Woman's Bracelets
There's a lot to be said about the real-world efficacy of Wonder Woman's Lasso of Truth, but the same can't be said for her Amazonian bracelets. In the comics, these weapons can be used to deflect bullets, withstand energy blasts, and cause destructive concussion waves by slamming them together.
That's fine for a person with incredible powers like Wonder Woman, but the average human wouldn't get much use out of them. Deflecting bullets would require superhuman reflexes, for one. Worse, a human being who successfully managed to generate a blast wave using the bracelets would probably rupture from the inside out, to say nothing of others in the vicinity.
The Green Lantern Ring
The power of the Green Lantern rings is certainly formidable, and perhaps one of the strongest weapons in the DC universe. While the overall premise of the ring is fairly straightforward, the real world application would be wrought with difficulties.
The biggest and most obvious disadvantage is the ring's ability to affect anything coated with the color yellow. This is a fairly large bug that could be exploited by anyone with a few buckets of yellow paint lying around. In the comics, the Lanterns were able to circumvent this weakness to some degree, but no truly effective solution has ever been brought to the table.
Mister Freeze's Ice Gun
Mr. Freeze is both a tragic villain and a ruthless monster, and his choice of weapon signals the latter. Case in point, the ice gun is one of the cooler (no pun intended), yet impractical weapons in the DC Comics arsenal. The gun has the ability to freeze objects or people into solid blocks of ice, which is done through a regulating mechanism attached to Freeze, and connected by a large cable.
In the real world, this weapon wouldn't get much play due to the laws of physics. However, Captain Cold's freeze gun does have links to real-world theoretical science, which has already been used to create weather manipulation technologies that make use of lasers to knock electrons out of their orbits, causing temperatures to plunge almost 120 degrees in mere seconds.
The Kinetic Hammer
The superhero Steel uses his kinetic hammer to great effect in the comics, but it wouldn't get much use in the real world. The hammer's design increases kinetic energy damage the farther it is thrown. It hurled over 60 yards, it can generate enough power to rival even Superman, himself.
Naturally, this would be the hammer's greatest weakness in a real world setting, as few, if any humans on Earth could successfully hurl a hammer that far. World record hammer throw Olympians average 63-95 yards, and that sport relies on a much different technique. In a fight, it's obvious no human being would have the combination of strength and accuracy to make it work.
The Stasis Square
The villainous Weapons Master supplies arms to various supervillains in the DC universe, but not all of his gadgets are worth the the investment. The most impractical of the bunch is undoubtedly the Stasis Square, a weapon which traps and immobilizes an enemy, while inflicting excruciating pain.
In the real world, subjects would either out from the pain, or suffer cardiac arrest if it went on too long. Unless the objective was to torment the subject for as long as possible before death, this would serve no practical purpose except to signal how sadistic and cruel a person is.
Batman's Grappling Gun
The heroic Batman battles a dastardly array of dangerous villains using a variety of gadgets, including the ever-popular grappling gun. He uses this particular item most often, and it can be deployed as a weapon if need be. The trouble is, it wouldn't get much traction in the real world. For starters, the person wielding it would need to be extremely fit when using it to ascend or catching themselves during a potentially fatal fall.
When used offensively, the Grappling Gun can ensnare targets, but the fictional application just wouldn't hold up for real. Movies, cartoons and comics feature Batman using the gun with pinpoint accuracy to catch criminals by the ankle or torso, which defies the laws of physics in almost every way.
The Atomic Arrow
It goes without saying that an arrow tipped with an atomic warhead is bound to create a mess, making it one very impractical weapon. Not only would physics fly right out the window in a real world setting, but nobody in their right mind would want to fire one off.
The Green Arrow used two variations of this weapon to stop Starro and Amazo, with differing results. If used in a conventional setting, such a weapon would kill thousands of people, cause immense damage, and send radioactive material into the air. It's a bad idea in a long history of bad ideas.
Black Canary's Canary Cry Bombs
It's no secret that military engineers have a number of sonic weapons already in development, or deployment around the world. In fact, the use of sound as a weapon is quickly becoming a hot button topic altogether. However, comic book sound-based weapons tend to be cut from a far less concerning cloth.
The Black Canary is a superhero that doesn't make a whole lot of sense, and her Canary Cry Bombs are a perfect example as to why. Theoretically, sonic bombs can be created, but they would either be too quiet, or far too catastrophically destructive to work properly. In the real world, the hassle would be too much.
The Miracle Machine
Comic books have a tendency to create weapons and items that defy not just the laws of physics, but reality itself. That's part of the fun, but it can go to extremes with weapons like the Miracle Machine. This device has the power to convert thoughts into reality, based on the will of the .
The machine is impractical, however, due to a fatal flaw - the actual . If at any time a person thought about dying, killing another, or some other horrible action, the Miracle Machine would make it a reality. Given the dangerous nature of the human subconscious, it's doubtful the universe would survive for very long.
Ring of Volthoom
Rings seem to be a common theme in the DC universe, but not all are alike. Some, like the Ring of Volthoom are highly lethal to the wearer, making them a counterproductive choice. This particular ring is just as impractical in comics as it would be in the real world.
As opposed to the Green Lantern rings which draw from a bearer's willpower, the Ring of Volthoom feeds on their fear. As the fear lingers, so too does the ring grow in strength, until it sucks the life right out of them. It's a pointless weapon that would break all but the strongest and most evil wills.