With 4 films currently residing in the chrome coated sci-fi franchise, and likely more to come, it's no surprise that over the years some seriously weird and wonderful devices have spawned from the Men In Black props department. Interestingly enough, most of the weapons used by the MIB throughout the films are entirely original, as in the graphic novel Agents K and J are equipped with traditional human firearms.
In the context of the films, though, many MIB weapons are repurposed versions of alien technology. As a result of Men In Black director Barry Sonnenfeld not wanting aliens to look like what "humans perceive them to be" the props in the film had to follow suit, sporting subversive appearances. Subversive in that many of them are far more powerful than they appear, here are the strongest among them.
MIB Standard Issue Firearm
The opening sequence of the original Men In Black is an amazing example of grabbing the audience's attention and introducing them to an outlandish concept. It begins with Agent K taking control over an illegal immigration bust away from a regular police officer while tracking down Mikey, an alien posing as one of the immigrants.
Following Mikey's unmasking, he attacks the police officer and K is forced to shoot him with his Standard Issue. It obliterates Mikey with some sort of energy blast but at the end of the day, there's a reason the Standard Issue Firearm is, well, standard-issue.
Neuralyzer
While at first glance many may not perceive the Electro Bio-Mechanical Neural Transmitting Zero Synapse Repositioner, or as Agent J refers to it, "Flashy Thingy", as a weapon, it most certainly would be in the wrong hands and a dangerous one at that.
Its primary function is to erase the memory of its target over a designated amount of time and replace said memory with a new one, most commonly one lacking a run-in with the MIB or an alien. In the final moments of the first film, J uses this on K to erase his entire career. While it may not be deadly, the Neuralyzer definitely wields a lot of power over its targets.
Reverberating Carbonizer With Mutate Capacity
"You sold a Reverberating Carbonizer with mutate capacity to an unlicenced cephalopoid, Jeebs, you piece of..." judging by that reaction from K when he sees what Jeebs is selling, we can guess that the Reverberating Cabonizer with a mutate capacity means serious business.
It's seen briefly in use by the previously mentioned cephalopoid at the beginning of the film when NYPD Officer James D. Edwards (Will Smith) is in pursuit. It charges up a shot and is subsequently dropped, bursting into green flame and dissolving into nothing. If that's what it does when it breaks, we don't want to see what happens when it fires.
The Series 4 De-Atomizer
Agent K's go-to choice whenever he needs larger firepower than his standard-issue, we see him use it exclusively in the first film. Once while in pursuit of the Bug, following the diamond store robbery, and once in the film's finale when he is eaten and subsequently blasts his way out.
When out of its human skin, the Bug is a massive alien life form capable of withstanding some serious damage. So when Agent K blasts his way out of it, causing quite a large mess, the weapon he uses should probably be afforded some respect.
Wing Mirror Blaster
Men In Black: International, saw a reboot of sorts for the franchise and two new agents in Chris Hemsworth's Agent H, and Tessa Thompson's Agent M. During the course of the film they become embroiled in a firefight and take cover behind their car. Turns out it's also a rolling armory.
Following Agent H's instruction, Agent M uses the car's wing mirror to dispense an unnamed blaster. She fires into enemy cover, completely and instantly disintegrating it. The only reason she doesn't dispatch her foes the same way is because of their speedy healing. We can't help but feel that against anyone else, this weapon would be a little overpowered.
Tri Barrel Plasma Gun
Nicknamed "The Jackhammer" we see this weapon wielded by J in the finale of Men In Black and again in the weapons locker behind the wall in Agent K's old house in Men In Black 2 with a new lick of chrome paint. Put simply its a big gun that shoots a loot of plasma to destructive effect.
Not enough for you? It's noted in some MIB extra material that the Tri Barrel Plasma Gun is capable of leveling a city block and is the go-to weapon when facing a rampaging Elephantite. If you don't know what that is, neither do we, but it sounds big so this weapon must be pretty powerful.
Exhaust Pipe Mini-Gun
In the same scene from Men In Black: International as mentioned earlier, the wing mirror isn't the only place that Agent H's ride hides some badass weaponry. As the fight escalates, Agent H assembles a Plasma Tommy Gun from the car rear and a hub cap, then instructs Agent M, "Exhaust pipe."
What's in the exhaust pipe? A purple laser spitting minigun. We only see it used briefly but it does some serious damage, carving through metal and displaying a lighting fast rate of fire. If it wasn't used against a couple of regenerative henchmen the fight would likely end before it started.
Noisy Cricket
A peppy little blaster that shoots a bolt of energy with enough recoil to send exactly one Will Smith soaring. We only see it used a couple of times in the first film, but it hits its targets with enough explosive power to evaporate metal and cause firey explosions.
Funnily enough, it's actually used exclusively by new recruits as a way for older agents to make fun of them, it's literally a joke, even in cannon. That doesn't take away its destructive capabilities though, and while the MIB may have a sense of humor, the Noisy Cricket is no laughing matter.
The Statue Of Liberty
In the final moments of Men in Black 2, the entire city of New York witnessed an alien spaceship escape to orbit and the final death of a giant tentacle monster, naturally, they need to be Neuralyzed. Evidently, one Neuralyzer wouldn't be enough to wipe the minds of the entire city, so Agent K just uses the Statue of Liberty, which is, in fact, a giant neuralyzer.
Take the power the regular Neuralyer has over the human brain and scale that by however many times bigger the Statue of Liberty is. There's a reason Agent J doesn't know about this piece of kit until the end of the second movie and that's because it's too powerful to be trusted to just any agent.
The Crystal Weapon
The MacGuffin of Men In Back: International is noted as possibly being the most powerful weapon in the galaxy. An example of this can be seen in the film when Agents H and M finally open up the crystal discovering the weapon's power source, a compressed blue giant star.
While the real-life repercussions of this would likely make the crystal weapon's mass impossible to lift, it's likely some sci-fi tech makes it all manageable. While in the desert the two Agents fire the weapon at a sand dune, carving out a Grand Canyon-sized crater. That was at a setting of 0.001, making this the strongest MIB weapon by far.