Mobile Suit Gundam has the Solar System, effectively a futurized version of the Archimedes mirror concept: it uses tens of thousands of giant mirrors, all coordinated by computer, and has enough power to blow a chunk out of a space fortress made out of solid rock. Mobile Suit Gundam 0083 introduces the improved Solar System II, which has much better control software and therefore doesn't require as many mirrors to achieve the same effect.
This trope receives a Shout-Out in The Crimson Badger, a Redwall fic, of all places, where Urthblood idly ponders about the possibility of creating a giant focusing lens that could incinerate an enemy army after having seen some children burn insects with a magnifying glass. He never comes around to building one, however.
According to the Friendly Four from the Darkwing Duck fanfiction Negaverse Chronicles, the "I Have a Death Ray" plans are one of the top three most common super villain schemes they have to deal with, along with "Take Over The World By Collecting a Resource" plan and "Let's Make a Shrink Ray."
Gyro later builds what he calls an "Atomic Death Ray."
It's hard to say which is truer to Wells' original idea. The original novel's heat ray was described as being invisible and a straight, thin line of heat. The former got the "heat" part right, but the latter got the "straight, thin" part right.
The film Danger Death Ray had a death ray, briefly. But it was mostly just vaguely European guys, some guy named Bart Fargo, and a catchy theme song.
Remember, it's a peace lovingdeath ray.
In the Mystery Science Theater 3000 episode featuring the movie, Tom Servo builds one, proclaims it's for peace... then proceeds to blast Crow with it because he was right there.
It Came from Outer Space (1953). The protagonist is uncertain whether he should believe the aliens' claims that they're simply trying to repair their spaceship so they can leave Earth. After a deadly confrontation with an alien guard who tries to slice him in half with a handheld Disintegrator Ray, he enters a chamber and is shocked to find the aliens assembling what appears to be a classic giant Death Ray, but actually turns out a device for powering their ship.
In The Pink Panther Strikes Again, Inspector Dreyfus uses a Death Ray to hold the world for ransom. It disintegrates too cleanly for Dreyfus's tastes: "I want a crater! I want wreckage, twisted metal. Something the world will not forget!"
Pretty much a staple in sci-fi movies since the '50s - the cheap B-movie Teenagers from Outer Space gave the invaders guns that instantly reduced humans (and dogs) to bleached skeletons.
For sake of reverence and posterity, the Martian Heat Ray in The War of the Worlds, by H. G. Wells, and all of its subsequent adaptions. Notably, it's a Heat Ray, and victims catch fire and burn to ashes, rather than just dropping to the ground. It's incidentally one of the best descriptions of a directed energy weapon in fiction: a completely invisible and narrow beam that just dumps it's energy on what it hits with no unnecessary flashiness.
The Killing Curse, Avada Kedavra from Harry Potter is a proper Death Ray, which kills a living being without even leaving a burn scar, but breaks statues. Note that side effects such as this seem to be pretty common in the Potter 'verse, at least in the movie versions — every single aggressive spell throws its target through the air, no matter its actual use. Harry is known as the "Boy Who Lived" because he is the only person in the wizarding world to survive this spell.
The Dragonback novels, by Timothy Zahn, feature a Death Ray, appropriately named "the Death," which ignores any defense and leaves anything unliving unharmed, but leaves anything hit by it dead, but not visibly hurt.
In Dan Simmons' Hyperion Cantos books Death Ray weapons, created by the mysterious AIs of the Core, are exclusive to officers of FORCE, the military of the Hegemony of Man. Nobody quite knows how they work and there are no visible effects, but they undoubtedly kill anyone targeted by them. Later the smaller gun-type weaponry is joined by ship-to-ship Death Rays that work at interplanetary distances and even a Death Ray bomb, which is supposedly capable of killing anything withing several light years.
Project X (later named the Thompson Harmonizer) in Atlas Shrugged, which emits sound waves capable of destroying anything within 100 miles.
Arthur C. Clarke wrote a short story involving a scientist who decided to murder his unfaithful wife with an improvised death ray. The ray was merely a beam of ordinary light, amplified by being projected through an observatory's telescope, with the intent that it'd dazzle her eyes while driving on a mountainside road, causing her to blindly go over the cliff. The narrator told the story to contradict someone who'd argued that any real death ray would be invisible; this one had to be visible to work.
"It was a ray, and it killed someone. What more do you want?"
Elleston Trevor, who usually wrote spy thrillers or mysteries, featured a death ray in the book Rook's Gambit. The hero became aware of a series of mysterious deaths of people who'd been sentenced to execution but simply fell dead before the government could kill them. The weapon was hand-held, with a range "limited only by the curvature of the earth," and made no noise or flash.
Subverted in Anathem: Erasmas sees red light shining from the sky on part of his concent and panics, thinking that it is being shot at with death rays... then his scientific training kicks in a few seconds later as he realizes that any such ray would naturally be invisible.
John Ringo's Troy Rising series has the main character creating orbital mirrors to collect and concentrate sunlight to use as a mining laser and weapon. Referred to as a "Death Ray" by the main character, it could pump out 170 Petawatts of power by the end of the second book, blowing through even the strongest shielding and armor as if it were tin foil.
The fairies' bio-bombs in Artemis Fowl give a flash of blue light, killing every living being in it. All inanimate objects are unharmed. Except from Holly's LEP-helmet, which she uses to absorb the full blast of a bio-bomb meant to kill her.
In The Chronicles of Professor Jack Baling Jack’s first invention as a mad scientist is one of these. Extra points for being housed in his wife’s hair dryer, so not only can it convert a kitchen island into ash with a red beam of light, it does so while being pearlescent pink with stylized purple flowers.
A 1927 Russian novel by Aleksey Tolstoy (relative of Leo Tolstoy) called The Hyperboloid of Engineer Garin (AKA The Garin Death Ray) has the titular engineer invent a device which focuses beams of light using two hyperboloid mirrors into a single destructive beam, which can, at full power, obliterate a warship on the horizon. Naturally, he uses it to try to Take Over the World. Which is a mistake, as hyperboloids don't focus light rays into a single point. Paraboloids do. Also, that only works if the incoming rays are parallel.
In a Star Trek Expanded Universe novel, The Last Stand, Riker and Troi infiltrate a Kreen generation ship in order to find out their plans. A Kreen engineer takes a liking to Troi and shows her a "secret project" designed to help them defeat anyone (presumably, even the Enterprise). It looks vaguely like a weapon. Troi, in an attempt to get more information, asks if it's some sort of "death ray". However, it turns out that the Kreen leaders have known about Riker and Troi and have deliberately set up the "weapon" (which is nothing more than a telescope with added junk to make it look like a weapon) to convince them and get them to return to the Enterprise. The real weapon is a virus that was meant to infect the Enterprise crew. What the Kreen didn't count on was the transporter bio-filters detecting and removing the virus during the beam-out.
The Laundry Series by Charlie Stross features basilisk guns. Actual basilisks and gorgons in this 'verse are certain creatures or humans with an Eldritch Abomination-linked tumor in their brain; spooky observer-effect magic means that instead of shooting out a beam of death, whatever is observed by them instantly has a percentage of its carbon atoms converted to silicon. The results are invariably lethal to living beings. So naturally, the titular agency figures out a way to duplicate the effect with a pair of ordinary video cameras, linked to some very special software that emulates the effects of the basilisk tumor; a basilisk gun to the face can even kill a shoggoth.
Although rare, this is how laser pistols work in Firefly. Too bad bullets are still better (and way more common).
The Daleks in Doctor Who have Death Rays, which were once most literal instances of this trope - any living being struck by it goes into X-Ray Sparks and dies screaming, then and there, wheareas the rays never caused serious damage to property (missing a target results in a minor spark burst.) However, as of "The Stolen Earth," a small group of Daleks showed that they were more then capable of destroying a building, although they did have "Maximum EXTERMINATION" setting on. The result was an impressive boom.
The Dalek extermination effect has gradually got more elaborate over time as special effects improved. At first you simply saw an emittor extend from the Dalek gunstick in close-up, followed by a quick cut to the victim as the whole screen goes into negative. Victim screams and drops dead. Things got gradually more elaborate over the years, especially when it became possible to add ray effects to the screen, but the X-Ray Sparks effect wasn't introduced until the last pre-2005 appearance, "Remembrance of the Daleks", where it was quite elaborate for the time and budget.
In their very first appearance, the Daleks do shoot to paralyze. Once. This was before they got on their EXTERMINATE kick. But after that one incident in the second serial of Doctor Who ever, Daleks do shoot to kill.
There's been mention that the Daleks' weapon could kill instantly and painlessly, but they deliberately dial down the power of their weapons depending on the species encountered so it takes longer for said being to die. Yes, the Daleks so freakin' evil they have a Death Ray and Agony Beam in one convenient package!
They did explain what a Dalek neutralizer ray does, and why nearly everyone hit with this screams in agony as they die. The Doctor called it "internal displacement": Your internal organs are scrambled, literally. Now imagine what would happen if Doctor Who stopped trying to be family friendly with the special effects...
Though the fact that the ray can be conducted through water suggests it's actually some kind of electron particle beam.
The Daleks do shoot to stun in Planet Of The Daleks.
In Asylum of the Daleks, the Dalek ray, complete with iconic sound effect, is used to stun the Doctor to bring him to, basically, Dalek city hall. The same presumably goes for Amy and Rory.
Death Rays are actually extremely common in Doctor Who. Hardly an episode goes by without some innocent being disintegrated or otherwise killed by a bad guy, usually with some type of energy weapon.
The Varon-T Disruptors in Star Trek: The Next Generation were a "modern" Death Ray, they disintegrated the target like a normal disruptor... but did so slowly, causing tremendous pain. Only five were ever produced before the Federation banned them.
And a small note: even though they don't usually use it as such, the normal hand phaser in Star Trek does have a disintegration setting, which would make it a Death Ray as well.
Seen in the Star Trek: Voyager episode "Tinker, Tenor, Doctor, Spy" with the Photonic Cannon, a Weapon of Mass Destruction from the Doctor's daydreams powerful enough to take out a Borg Sphere in one shot. This is later successfully used to bluff aliens who thought it was real.
In "Future's End," Braxton's got a sweet Disintegrator Ray. Straight out of TOS, anything hit by it just sizzles and is no more, without even the slightest damage to the surroundings. Again, though, Federation phasers are capable of this on max setting.
Naturally given that it's a homage to cliched sci-fi, Mad Scientist Dr Chaotica has to have his fiendish Death Ray in the holodeck program The Adventures of Captain Proton.
Chaotica: "But my greatest achievement is there. Behold: the Death Ray."
Carter: It's a ray that causes immediate death! Why can't you just say "death ray"?
MythBusters examined whether Archimedes created a death ray using many mirrors focused on a single point. Three separate tests came to the same conclusion: Archimedes didn't. At most, the Greeks likely used the light reflected from the mirrors to dazzle the eyes of the incoming Roman invaders.
Jamie: Something seems to be wrong with our Death Ray. I'm standing right in it, and... I'm not dead yet.
A That Mitchell and Webb Look sketch featured a Mad Scientist demonstrating his "Giant Death Ray", along with a "Giant Laser-fitted Armored Scorpion Of Death" - turns out his name is Professor Death, and he's horrified at the President's asking if these (obviously lethal) machines might have military potential. His intention is for the Giant Death Ray to be the world's first bar-code reader — or, with the power turned up, the world's first laser eye surgery device. The scorpion's tail fires only "helpful bullets." They then of course push the idea to silliness: "No! I created the Doomsday Bomb to help mankind, not destroy it!"
Sheldon from The Big Bang Theory tried to build a "sonic death ray" as a child. Apparently all it did was annoy the dog.
In an episode of "The Saint" a defecting Soviet scientist is murdered with his own weapon for the secrets of the death ray he has just invented; at the end of the episode, the killer runs away with the only working prototype; he trips, falls, drops the device, the beam accidentally activates, and....
The Murdoch Mysteries episode "The Tesla Effect" goes full Teslapunk (including an appearance of the man himself), with a Victorian microwave weapon.
Doe Deer by Crystal Castles consists solely of Alice Glass screeching "Death Ray" over and over.
"Weird Al" Yankovic's "Slime Creatures From Outer Space" will "zap you with their death ray eyes / blow you up real good!"
A cartoonCharles Addams did for The New Yorker shows two men standing at the upper-story window of a patent office, one of them holding a futuristic gun which is plugged into a wall socket. The caption reads: "Death ray, fiddlesticks! Why, it doesn't even slow them up."
Members of Task Force: VALKYRIE in Hunter: The Vigil can requisition a weapon that is, essentially, the Medusa Particle Beam Cannon (see below). It takes a lot of energy to run, but does a hell of a lot of damage.
Also from World Of Darkness, we have the fanmade game Genius The Transgression. Since it's about Mad Scientists, it's only to be expected that death rays are an easy-to-make, commonly occurring Wonder.
The Finger of Death spell from Dungeons & Dragons is essentially the magical version of this.
Beholders, catoblepae, and many other monsters produce their own death rays naturally. And the traditional pistol-shaped kind show up in the 1e AD&D module Expedition to the Barrier Peaks and the D&D Blackmoor adventures.
GURPS: Ultratech has a slew of them from a half dozen weapons that disintegrate the enemy to Mind Disruptors that make the target's body want to die.
In Master of Orion series, the Death Ray is the signature armament of the Guardian of Orion, and can only be obtained by beating the Guardian and looting the ruins on the planet below. (Or trading with/stealing from/conquering someone who has.)
In the second game, successfully capturing an Antaran battleship and researching its equipment can also yield Death Ray tech.
And of course the alien ship in Fallout 3. Its Death Ray can be fired towards Earth and cause a massive mushroom cloud. Not to mention that the Lone Wanderer used it to blow away the other alien ship.
NetHack's wand of death sends a ray of death towards an enemy who will instantly die except under a few extenuating circumstances (the ray misses, the target has magic resistance or reflects the ray, or is polymorphed into an undead or demonic creature, or is Death).
NetHack also has a wand of disintegration, which has similar results if the target isn't immune. (Important safety tip: don't shoot either of these wands at yourself or at a wall near you.)
A death ray appears in the final mission in Advance Wars 2: Black Hole Rising. Ironically, it can't kill units, only reduce them to 1HP.
So more of a Near Death Ray then.
Considering units have 10 HP, I believe the proper term is Decimation Ray.
Surely a decimation ray would reduce their HP by 1 not to 1?
The enemy spell "Calmness" ("Repose" in the Updated Re-release) in Final Fantasy VI is a beam of pale blue light that descends on a character, and kills him instantaneously regardless of defenses.
You can buy and mount one of these on your plane in Raptor: Call of the Shadows. It's one of three laser weapons with instantaneous blast (the others are a laser turret and a twin laser).
In EarthBound, Jeff (one of the heroes) gets a Death Ray as a weapon.
The Marathon trilogy features the Trih Xeem, the 'early nova device' actually used by the Pfhor at the end of Marathon 2. It seems to do what the name implies, cause a star to go nova which would wipe out pretty much anything of consequence in the surrounding system (the planets, moons etc would probably still be there, just with their surfaces pretty much scoured and then left uninhabitable). It is implied that the Pfhor, being the nice caring slavers they are, give this weapon to all their main battle fleets for use as a last resort in hopeless military situations.
In The Legend of Zelda, Link or Zelda receive Light Arrows at the end of many games. These act as death rays, killing any monster in one hit, while shattering inanimate objects.
In World of Warcraft players who learn the engineering skill can make a 'Gnomish Death Ray', which drains the user's health before firing. It's not a guaranteed kill, but being hit by it hurts, to say the least.
Nexus: The Jupiter Incident has one example. When the Vardrag-Noah alliance invented the fortress shieldnote huge, spherical shield that is completely impenetrable to outside fire yet allows friendlies inside to fire out; taking it out requires either tons of firepower to overwhelm it or quick wits to be inside it's radius when it activates to protect their supply ships, the Gorg answered with the Siege Laser: a giant Wave Motion Gun affixed onto a battleship. It requires three other ships to assume a triangular formation around the battleship and provide power but when it does fire, the results are very painful for the target.
The Gorg later give the technology to the Noah colonists, when the true culprits of the Cataclysm are revealed. It proves to be the only weapon capable of damaging the Locust Queen.
The mod Unreal4Ever for Unreal Tournament has a comparatively small laser pistol that shoots a continuous, hitscan stream of energy. Killing an enemy with it will cause their flesh to boil instantly, leaving behind only a charred skeleton. Can be upgraded by picking up more of the same gun; at its most powerful it really embodies this trope, as casually moving the beam across an enemy will kill them almost instantly.
Future installments of the series would provide the link gun, whose alternate fire does pretty much the same thing as the above weapon.
In Sunrider, Veniczar Arcadius' flagship, the Legion, comes equipped with one of these.
Starcraft II's Colossi fire these in pairs, sweeping them in a line of damage for all biological units. It's called a Thermal Lance, but come on, the Colossus is a four-legged strider so tall it can be targeted by both ground and air units, we know what it is. They were sealed away in asteroids after they were used in a colonial revolt by the Protoss in a My God, What Have I Done? moment.
The Stone Zealot, a giant stone statue of a Zealot, fires the exact same thing, though now called Eye Beams.
The Squiggoth in Dawn of War has a Zzap gun mounted on its back that does huge damage to any unit including vehicles. It's a shame that like all orks, you stand a better chance of hitting something with by grabbing it by the barrel and taking a swing.
It's almost a rite of passage for an evil Spark (and a number of non-evil ones) to make a Death Ray, like the following exchange shows from this strip shows.
Agatha: What about a good death ray? That'd be perfect! Gil:I don't have a death ray! [...] Agatha: So what you're telling me is that you—Gilgamesh Wulfenbach—the person next-in-line to the despotic, iron-fisted rule of the Wulfenbach empire—have got no weapons powerful enough to destroy those things. That's just great. What kind of an evil overlord are you going to be, anyway? Gil: Apparently a better one than I'd thought...
Agatha herself seems to have a fascination with death rays if going by the numberoftimes she can be cited using her immediate materials wishing for/building one. Her current one shown here...well, if you're looking at the damage to the wall, you're not looking far enough.
One strip of Casey and Andy features a ray gun called the Kill-O-Mat. While this one doesn't work, the Casey Vaporiso-Annihilatomat does wonders.
Narbonic has Dave get killed by one. Why did you do that, Dr. Narbon? "I had a death ray." But it's more complicated than that...
In S.S.D.D the Tower of Babel almost counts as the planetary version, as it's a skyscraper sized maser cannon that can roast everyone in an anti-missile defense base (though the base itself appeared intact). The way things are going it's likely to be destroyed before it's used to destroy another country.
One Packrat strip features the MAD-Ray (Memorymoog Acoustic Death Ray).
Pi: "Hyperspace death ray" is completely logical! Credomar was built before teraports, and is too big for wormgates. That means it had to be fired where it was built. Now...since it's not sharing the system with anything worth attacking or defending, it was never meant to be fired at local targets. Ebby: Okay...I guess firing through hyperspace makes sense, assuming it's even possible. But...death ray? Pi: It sure isn't gonna launch prayer beads.
Norman of Dragon Tails at one point attempts to use an ion cannon apparently capable of wiping out an entire city to destroy Enigma. It, of course, does not go as planned.
Dr. Horrible converts a Stun Ray into a Death Ray to use against Captain Hammer. In the end it is damaged after Captain Hammer punches him and it ends up exploding, causing Captain Hammer great pain and killing the Wide-Eyed IdealistLove Interest Penny.
Earlier, he takes umbrage at Johnny Snow calling it a Death Ray.
Commander Nebula: What's the difference between that and a normal death ray?
LGM: More death.
We can't get there in time to stop it! What're we gonna do?
An episode of The Simpsons showed Frink with a death ray he was developing, although it was only capable of generating a beam which felt pleasantly warm (plus he gave up on it when he failed to secure funding).
...He shouldn't have admitted that "well, the ray only has evil applications..."
The Venture Bros. have a lot of these but in the episode "The Lepidopterists" we find Jonas Jr has inherited a very nice one. Brock and the OSI guys are all very impressed. "If that [death ray] was a woman, I'd marry her" "And I'd jeopardize our friendship by nailing your wife"
Dr. Venture has accumulated more than he needs - Brock is worried he's too unconcerned about the security problems at a yard sale, pointing out he put up a 'Laser Death Ray Bargain Bin'.
One of the unproduced episodes of Invader Zim had Zim instruct GIR to activate a Death Ray (or a Doom Ray, to proceed with his latest plan. It works, and GIR takes over the Earth while Zim is having his existence evaluated.
Varrick accidentally creates one in Season 4 of The Legend of Korra when experimenting on some spirit vines. It's capable of punching clean through the rear of the train he's on, and even does major damage to a nearby hill. This freaks him out so badly that he immediately shuts down the project, but unfortunately for him Kuvira has other plans.
It is said that Nikola Tesla actually built a prototype of a tower that could kill anything within a certain radius. For some strange reason, the military wasn't at all interested when he pitched it to them. He called it a Peace Ray, rather than a Death Ray, of course. Despite the name, it was actually closer to Some Kind of Force Field. It was supposed to create an electromagnetic bubble around an area and anyone that tried to pass through would be electrocuted to death. The idea was to deploy them around every country to create world peace by making it impossible for anybody to invade anybody else's land. Also, like nearly all of Tesla's ideas post-1914 or thereabouts, it didn't work.
The Medusa Particle Beam Cannon, which is currently in the late stages of development and is going to be used in a field test soon, if successful, will result in the creation of what is essentially a real-life portable Death Ray.
The MTHEL, on the other hand, has already had functional prototypes built, capable of shooting down not only missiles but artillery shells and mortar shells, feats almost no other weapon can do. Because of the precise details of how high-energy lasers work, the MTHEL wouldn't be able to kill a person easily (though it would cause serious harm) - but it can destroy small, fast-moving explosive projectiles more accurately, and less expensively per shot, than any other current weapon.
Neutron Bombs are essentially nukes that emit more Death Rays and slightly less Kaboom than their more conventional cousins.
For the technically minded: about 50% of the yield is in the form of high energy (20MeV) neutrons, compared to about 5% of a standard thermonuclear bast which produces about 5% of its yield as thermal (2MeV) neutrons.
Often misunderstood as an antipersonnel weapon that would kill humans but leave buildings standing, the basic 1kT neutron bomb design would destroy non-hardened structures in a mile-wide blast. All unshielded humans within a two mile wide area would receive a lethal radiation dose. A conventional nuke of the same size would still kill everyone in a two mile wide area, but by crushing and incinerating them. An airburst neutron bomb might not level a city, but would still do a vast amount of property damage.
The original use for the neutron bomb was against neither cities nor people but tanks. Tank crew were well shielded from nuclear blasts and radiation, but a sufficiently high dose of highly penetrating radiation (such as high energy fast neutrons) would both incapacitate and fatally irradiate the crew, but also render the tank shell dangerously radioactive and therefore unuseable. Modern tanks are far better protected than those of the 60s, and a neutron bomb would have to be detonated so close to them that using conventional nuclear explosives would be just as effective, if not more so.
The Pentagon's nuclear warfare strategy moved away from nuking tank formations some time before tanks became largely immune to these weapons, simply because herding an armour column into a nuclear killing zone is pretty impractical even if it were politically and ethically acceptable to make use of battlefield nukes.
Large particle accelerators can generate some impressively powerful beams, which would act like death rays if anyone wandered into the path. Luckily for them, the beams are usually kept in vacuum chambers, confined by powerful magnets. The only exception is when it comes time to turn off the beam, when it gets "dumped" into something so that it doesn't ravage the accelerator when the magnets come down. For the Large Hadron Collider, each of two beam dumps must be able to absorb 362 MJ of energy in 90 microseconds, for 4 TW of power. Since that would blow a hole clean through the tens of meters of metal usually used for that purpose at lesser facilities, engineering the LHC beam dumps was something of a challenge.
Who the hell hasn't tried to invent a death ray? Pretty much no one, it seems. Tesla! Archimedes! A bunch of crackpots!
Two French chemists named Pierre Joseph Macquer and Antoine Baume made a "solar death ray" in the 1750s, using a concave mirror of mercury-coated glass to melt grains of platinum in 1758 (which has later been duplicated with large lenses).
During World War 2, when German communications concerning the V-weapons were intercepted, British scientists viewed with deep suspicion Hitler's references to a "devastating weapon with which we ourselves cannot be attacked". The actual weapons referred to - early pulse-jet cruise missiles and ballistic rocket missiles - were several guesses below "death rays" on the scientists' list of suspects.
Another ray-weapon of World War II vintage which can and will kill something which is organic is the ubiquitous radar. If the radar waves (which are actually microwaves) can be focused on an organic target, they can fry it quickly. In normal conditions, radar waves are less focused and do not penetrate metal due to the way they work and do not have enough energy to kill, but very large radar installations may be very dangerous for their crews and anyone in close proximity.
Strangely enough the development of radar in Britain was spurred by this trope. In the 1930's the Air Ministry was bombarded with crackpot ideas for developing death rays that could be used to destroy planes or at least kill the pilot. Eventually the Air Ministry offered a public reward of 1000 pounds for anyone who could invent a death ray that could kill a sheep at 100 yards. At the same time discreet inquiries were made to two scientists, Robert Watson-Watt and Arnold Wilkins, as to whether such a weapon was indeed possible. The scientists easily proved otherwise, but in order to be helpful to the Ministry said that using radio waves to detect approaching aircraft was theoretically possible. Their paper arrived just in time to be considered by a committee on the subject of air defense, and the rest is history.
Lasers. Most aren't powerful enough to really count as death rays, but you really wouldn't want to stand in front of something like the Nation Ignition Facility's 2 megajoule laser system.