Turning a weapon, frequently a pistol, so its grip is horizontal rather than vertical.
Showy, flashy, and generally useless as a marksmanship technique. Normally recoil lifts the barrel against gravity. When firing in this manner recoil pulls the gun sideways instead and tends to turn the shooter around in a circle. Additionally, it makes the sights much less useful.
Visually, it emphasizes the fist of the gunner. In other words, Rule of Cool wins in fiction.
The technique has sometimes been used with specific guns for practical reasons. For example, it saw much popularity in 1920s China in conjunction with the Mauser C96, where the technique negated the pistol's awkward upwards ejection, and allowed automatic variants to more effectively sweep rooms. Wheellock pistols were routinely held this way to reduce the chance of a misfire. It is the safest method of firing the AK-47 when lying prone - due to its awkwardly large magazine, holding the weapon vertically elevates the angle of the barrel upward by a good 20 degrees, which means you have to lift your head well off the ground to look down the sights, presenting a large target for any hostiles and thus defeating the point of firing from a prone position.
Combine this one with Guns Akimbo, and you have something spectacular, but God help us all if it goes too far...More Dakka may be employed in an attempt to counter accuracy issues. To slice the Willing Suspension of Disbelief into little bits, have someone pull Offhand Backshots this way... and hit. Without suffering from a sprain and/or dislocated joint after this. A way to make Improbable Use of a Weapon. See also Reverse Grip, for edged weapons.
This trope, along with various other Hollywood gun styles such as Guns Akimbo, was examined by theMythBusters. They proved that both tropes are just as inefficient as you think.
Despite the similar name, has no relation and is not used in Gangnam Style.
Compare with One Handed Shotgun Pump, which is Rule of Cool similarly applied to shotguns.
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How Kirika in Noir occasionally holds her Beretta M1934. She fires her gun right-side up most of the time, but holds it horizontally when she runs or is going to run sideways.
Dutch from Black Lagoon fires a pump-action shotgun Gangsta style. Considering that he is a Vietnam war vet, he should by all accounts know better, but it sure looks cool. It might be justified because of his shades, having accidently gone into the gas mask routine from his army training, during that scene. (See Real Life examples) or, it may reflect the fact that that particular model occasionally suffers from feeding problems in real life, and that particular posture is recommended to ensure proper cycling. Played straight again when we find out that he never served in the military, or at least not in Vietnam.
The Strike Noir Gundam from Gundam SEED C.E. 73 Stargazer fires its laser pistols in this manner. Being a Humongous Mecha with computerized targeting systems, it's quite accurate, but there are still no advantages to shooting this way...other than the Rule of Cool, of course.
In the video game Alliance Vs. ZAFT II, the rapid shooting is just one of many factors that makes the Noir a Game Breaker banned from Tournament Play in Japan.
The season 2 finale has Lockon's Cherudim engaging Revive's Gadessa which destroys his beam pistol, blowing off the Cherudim's index and middle fingers. When Lockon finally corners his opponent, he pulls out his remaining pistol and fires it like this but upside-down, pulling the trigger with his ring finger.
Death the Kid from Soul Eater takes this trope to its logical extreme, holding Guns Akimboupside down, firing the weapons with his pinkies instead of the more conventional index fingers. He can be excused because he's a Physical God with OCD. Also, he sometimes uses them as tonfas, and holding it like that would give him more power (torque) in that sense. Also, damn if it doesn't look cool.
Holding them upside-down is also useful for blocking melee attacks, since, held right-side-up, one would either have to twist their arms uncomfortably or present their wrists and hands for slicing and dicing to block with a gun. Not that blocking a melee attack with a gun is realistic, but realism isn't important in a series like this. This is the same series where every hero's weapon is actually another hero who shapeshifts into a weapon, after all.
Natsuki from Mai Hi ME is fond of doing this with her pistols. They're very small, so they don't have much recoil to begin with, but hey...
Trinity Blood's second episode features Tres firing one of his guns held upside down, over his shoulder, in two directions at once, and yes, even this way. Of course, he is a combat android and can probably get away with that.
Mello of Death Note occasionally holds his gun like that, but since he never actually fires from this position it may count as a means of intimidation.
Kiriyama, from Battle Royale, only shoots this way. This is only in the manga; in the original novel and the film adaptation he shoots normally.
While giving a firearms training lesson, Rally Vincent gives a student who uses this style a thorough explanation as to why this is so prominent in movies and television: "The shell casings flying past the firer's face are 'a cool image', but without the sights, you can't hit anything." She does demonstrate that Gangsta Style is good for hitting targets flying through the air, as the bulk of the gun doesn't obscure the firer's vision as it moves upward or downward, by plinking a thrown can like a sporting clay - but then goes on to say that it's still a pretty useless technique, as targets on the ground move sideways, not up and down.
She also explains Guns Akimbo: "It's a throwback to old Westerns. The first revolvers could only be loaded or unloaded one round at a time, so shooters would fire six round from one, then switch. They only used them simultaneously in movies." She then proceeds to compare shot groupings by firing with two guns, then a two-handed grip. The two-handed grip gives her enough accuracy to cut a target in half. With a handgun. And by changing fifteen-round magazines just before she fires the fifteenth round from the first mag, she's able to fire twenty-nine shots in as many seconds!
She also gets chewed out by the owner of the firing range: he wanted idiots to line up and burn ammo with stupid shooting, and teaching them to shoot properly means they shoot less, and therefore buy less of his ammo.
You would think a well-renowned killer like Brandon Heat of Gungrave would know better than to exhibit this trope, but you'd be wrong. Notable in that he often uses two guns this way, with his arms crossed above the wrists. Imagine the potential for sprains and broken bones there... Even after dying and reanimated, he still does it—and capable of destroying enemies without even turning aroundto aim.
Nanoha of Lyrical Nanoha fires her magical staff using this style. Justified as 1: It's magic 2: She has a long staff shaft to deal with and putting that pistol grip in a proper vertical configuration would put the staff over her shoulder like a rocket launcher(giving the wrong impression) and 3: She's not using said Pistol grip to Aim her shot, she's using magical targeting systems.
Played for laughs, surprisingly, in Gurren Lagann, with Kamina pointing his pistol at a Beastman pilot in order to hijack a Gunmen of his own. Take note that he's holding the gun upside down AND pointed at himself. Luckily he never fired it. It was even funnier when before Simon assisted, he was trying to pry open the hatch doors with the same gun. AND of all the ways to use it, as a hammer, no less
Not shown is the character who's attempting to pull the trigger with his "Gene Simmons-like tongue"
A dime-store crook tries this in Ultimate Spider-Man. He misses completely despite being mere feet from Spidey, who actually complains that he didn't get the chance to show off by dodging.
Lampshaded in Warren Ellis' Ultimate Extinction. The Falcon has an incredibly cool scene where he rains machine gun fire down on a Silver Surfer drone, and yet manages to miss every shot. Misty Knight then berates him by asking how the hell someone can miss while firing two guns.
In The Mask, when the Mafioso and one of his mooks fire shot after shot at Ipkiss as The Mask, the mook holds his gun gangsta style while his boss holds it in traditional style. It doesn't make much difference, because the closest either of them gets to hitting him is grazing his pajamas.
In Date Night, Phil (Steve Carell) becomes MORE scared of having a gun pointed at him when it's turned sideways: "Kill shot! That's a kill shot!"
Subverted in Star Trek: Generations: Dr. Tolian Soran fired his energy pistol with the grip in a sideways position, but the gun itself and its sights automatically aligned itself to an upright position.
Alonzo Harris (Denzel Washington) in Training Day holds his off-hand gun in this fashion while spraying some gangsters with Guns Akimbo. This could be to prevent the left-hand gun from ejecting hot shells onto his right arm. .
In The Bourne Identity, Jason manages to disarm a mook by flipping the gun towards him (which would be a forward flip away from the mook), and then, without bothering to correct it, he sticks his pinky in the trigger guard and shoots the mook. He then comes under attack before he's able to correct the grip, and dual guns the other mook down.
Subverted in the Death Note live-action film. Naomi Misora fires her gun sideways at Shiori and manages to hit her (much to her shock and surprise). Shortly after, its revealed that Naomi had been shooting with the intent to miss, and had only been successful because Light had dictated with the Death Note that Shiori would die of being shot, and that Naomi would fire warning shots and commit suicide out of horror for having killed someone.
Near the climax of Malibu's Most Wanted, Brad fires a pair of machine pistols like this at a bunch of South Central street thugs. He doesn't succeed in actually hitting anybody, but he does send them running for cover.
Korben Dallas (Bruce Willis) in The Fifth Element holds his gun/blaster sideways when a mugger meets him at the front door. Since he's at point blank range, his accuracy isn't going to suffer, and he's just trying to scare the mugger off anyway. Intimidation factor of it all.
Apoc from The Matrix takes out several policemen in a shootout, with his Uzi turning sideways as he fires at them from left to right. This might make a bit of sense considering that the recoil would be pushing his gun across rather than above his targets' heads.
We see Keyzer Soze hold his gun in this way at the beginning of The Usual Suspects. This acts as a Red Herring later when we see Hockney hold his gun in this fashion later in the film. The filmmakers jokingly referred to this grip as "Nineties Style."
Invoked in The Green Hornet with an actual gangster, played by Christoph Waltz, who has his custom double-barreled gun upside down when he "punishes" a minion.
The police in RoboCop (1987), when shooting the titular hero after his brawl with ED-209. This was done (with sighted weapons, to be precise) in order to prevent hot brass cartridges from flying at the actors.
In Brotherhood of the Wolf, Fronsac fires two flintlock pistols this way during a target practice sequence. Hilarious in Hindsight if you know anything about flintlock weapons: not only would aiming them that way make an already-inaccurate weapon even more so, but they simply wouldn't be able to fire in that position.
In The Dark Knight Rises, when Stryver is attempting to kill Selina Kyle at the bar, he holds his pistol in this manner as a way to threaten her.
In Machete Kills, La Chameleón kills a guy while firing her gun with her pinky, after he gave a Last Request that his death be really cool.
Ironically, the only character in American History X to do this is Seth, a white supremacist. Its impracticality is shown in that Derek is able to disarm him with relative ease.
A street thug employs this style when threatening Jack in one of F. Paul Wilson's Repairman Jack books. Jack informs him that it's not a very secure grip ... and proceeds to prove it to the hapless lowlife.
In Roberto Saviano's non-fiction book Gomorrah, about the businesses, influence and actions of Camorra (a mafia-like organization active in southern Italy and particularly powerful in Naples) the author explains that one reason for the awkward length of some gang gunfighting throughout the city is that gang members, imitating movies, hold the guns sideways, resulting in poor aim (which combined with fighting behind cover results in nobody hitting each other for a quite long time).
Alas, the Andre NortonThe Time Traders book Firehand had the time travel project's weapons trainer, no less, use this technique (in a flashback) — in fact, it was presented as one of the clues telling the main character early on that this trainer knew her stuff. Ouch.
A character in Christopher Farnsworth's The President's Vampire turns his gun sideways, counter to what his instructor told him again and again, and the hot casing is ejected into his eye.
In an episode of Burn Notice, Michael infiltrates a gang in order to help a member get out without putting his family in danger. When Michael is given a gun in order to rob a dry cleaners, his associate corrects his handling of it, turning the gun sideways. Michael, who is certified on pretty much every firearm known to man, winces appreciably.
Law & Order: Criminal Intent mocked this, when the detectives are instantly able to identify a murderer as being an amateur - because the location of fired bullets demonstrate that when he tried to hold his gun sideways, he quickly lost control and started shooting everywhere but his target. The cops even point out that this was foolishly done in imitation of "gangsta flicks."
Played with in an episode of Diagnosis: Murder. Dick Van Dyke's character Mark Sloan is at a gun range being shown how to use a pistol. He fires off a few rounds normally (with realistic loudness and recoil) and then asks the man who was showing him whether he could fire it sideways "like on TV", twisting it to the side to show him what he meant. While the instructor starts saying why it's a bad idea, Mark fires the gun anyway by accident and the recoil flings it out of his hand with great ease and force - which creates a big enough diversion for another character to sneak past.
Ryutaros/Gun Form from Kamen Rider Den-O sometimes uses this. Perhaps because this is his preferred style, his aim is terrible. Considering his Chinese Dragon motif, this may actually be a reference to the Chinese example above, rather than Gangstas.
One of the mafiosi on The Sopranos berates a new guy for holding his gun this way, during a truck hijacking.
Used in a sketch on Mind of Mencia, wherein Carlos taught gang members to be more effective. After being corrected one remarks "Wow, it lines up and everything!"
Daiki Kaito/Kamen Rider Diend from Kamen Rider Decade shoots gangsta style just as frequently as he shoots properly (though only out of suit)—his aim is impeccable, either way.
In an episode of CSI: Crime Scene Investigation, Catherine Willows tells a smug gangster that this amateurish way of shooting caused a suspicious burn on the gangster's neck from the hot ejected shell casing, as well as leaving traces of the shooter's DNA on the shell casing.
The leader of the short-lived series "Acapulco Heat" had a variation on this. He held two pistols at once, but fired one normally and the other horizontally, lining them both up at once at a 90-degree angle. This is probably very unwieldy and not at all recommended for use in real life, but it's also the only way you could conceivably try to aim down both sights of two pistols at once while dual-wielding.
Sometimes done on The Wire, but anyone (cop or criminal) who actually knows how to use a gun will fire it properly, image be damned. Deconstructed in one scene where an inexperienced drug soldier suggests using a drive-by to attack a rival crew's corner ("yo, let's go all West Coast with this") because it looked cool in Boyz n the Hood. After they fail to hit a single rival dealer, one of his more experienced comrades steps out the car, calmly sights her fleeing target, and shoots him in the back of the head.
"Fuck them West Coast niggers, 'cause in B-more, we aim and hit a nigger, you heard."
Reese: Take you, for instance. You're holding the gun sideways. It'll eject the cartridge right into your face.
When MythBusters tested the "Blown Away" myth, the intro video showed a stereotypical hunt-the-fugitive scene, complete with Adam taking aim at fugitive-Tory gangsta style. But when you're not actually pulling the trigger note (Tory went flying courtesy of a special harness, a rope, and the rest of the team), it doesn't matter that this method is inaccurate. They visited it again when testing how effective various firing stances are. It didn't hold up all that well, greatly reducing accuracy.
One episode of NUMB3RS showed two gangsters firing their guns like this. They missed.
In The Newsroom, Will discovers that his date carries a pistol in her purse. After he removes the bullets, she points it at him to demonstrate what would happen to an attacker. He deftly disarms her and points her own gun back at her gangsta style, saying that this is more likely to happen.
In The Shield, the Strike Team robs an evidence van with bandannas over their faces and fake gang tattoos, and with their guns held gangsta style to reinforce the notion that the van was hit by a street gang.
This◊ bit of Stephen Colbert fanart (from this story). Given Stephen's obsession with doing what feels good rather than what makes sense, it's not surprising that when he snaps and decides to shoot up the set, he's going to do it Gangsta Style.
On a weaponry-themed Image Board, some anonymous posters had possibly Truth in Television pictures of gangsters in an African town shooting in all sorts of "gangsta" styles; it was mentioned that they followed a spray and pray principle and did it as macho posturing.
When LEGO first released their Star Wars line of toys, the battle droids had arms with only sideways hands, which caused them all to be holding their guns in gangsta style. It wasn't until the release of Revenge of the Sith that LEGO finally corrected this, but seeing a literal army of "gangsta" battle droids was pretty amusing.
Vampire: The Masquerade has "Gangsta Style" as a special attack. It has two drawbacks: reducing your accuracy and increasing the chance of a misfire, and provides absolutely no benefit whatsoever.
The New World of Darkness supplement Armory talks briefly about this trope, noting that it incurs massive penalties but could impress/intimidate people.
In Hero System's combat handbook, holding a gun sideways incurs a penalty on attack rolls but adds a bonus to Presence when attempting to impress people.
GURPS addresses this in "GURPS: Tactical Shooting" under "Things not to do". Specifically, all attacks are treated as "Unsighted Shooting" with all the usual benefits and drawbacks thereof. However, the stance encourages limp-wristing (penalty to Guns) and, if used with an automatic, increases the likelihood that the weapon will malfunction.
In Unreal Tournament, the secondary fire of the default Enforcer pistol is to increase the rate-of-fire and turn it sideways; the manual specifically calls it "gangsta style". Pick up a dropped Enforcer, and you can double the fun. Realistically, (if anything in UT can be called realistic) this does decrease your accuracy.
The beloved Enforcer returned in Unreal Tournament III and while there's no dedicated mode, keeping an opponent in the crosshair long enough will make your character automatically turn his gun(s) sideways.
It's carried over from Unreal, in which you could do the same thing. It's averted, however, since attempting it at anything less than point blank range will cause you to miss spectacularly.
Coyote Smith in Killer7 fires his gun this way. Con Smith in the same game combines this trope and Guns Akimbo, but then again, he's a teenager. A blind one.
Technically, Coyote holds it almost-upside down. Surely enough, the recoil is crazy compared to the other characters'.
Also, Con's blindness may be the cause of his side-shooting: it keeps his super-hearing turned toward his targets, and the iron sights wouldn't do him much good anyway.
Used by EVA in Metal Gear Solid 3: Snake Eater with her Mauser C96 (see below for the entry on that gun, under Real Life). The technique of turning a C96 sideways so the recoil guides your hand to the next target in a sweep is referred to as Bandit Shooting; Snake and Sigint have a discussion about using a Mauser this way.
In a few cutscenes in Metal Gear Solid 4, Snake cants his M4 about 45 degrees to the side to use a different set of offset optics, rather than what's mounted on the top rail. It's a real technique, but it's not very widespread. Another cutscene or two has him holding it the prerequisite 90 degrees, but in the former it's to keep shell casings from bouncing off his cover and hitting him, and in the latter he doesn't fire before control is given back to the player.
Towards the end of the game, a Navy man can be seen briefly with a canted weapon in one cutscene. Given that he's in the bridge of the good guys' sole functioning battleship, he may have it that way to easier clear the consoles and equipment.
In Perfect Dark, characters in single and multiplayer are able to do this - however, it only happens when they are right next to their target.
Local gunslinger Gilder from Skies of Arcadia shots this way for close-range attacks (though for him, close range means walking up to the enemy and dropping the gun right in the enemy's face). However, for long range attacks he uses the more practical two-handed grip.
Dante in Devil May Cry fires his twin pistols this way when firing while sidestepping. In addition, in the third game, he often turns one pistol or the other sideways if firing at separate targets in his Gunslinger fighting style. Also, in cutscenes, or if using gunslinger mode to fire at a single target, Dante will hold both guns sideways and hold his arms across each other, left gun on the right side, right gun on the left side. First done in the series at the end of the first game, coupled with Dante's Catchphrase: "Jackpot!"
Dungeon Fighter Online has a gunner class. Most of their shots are normal, but Multi-headshot and Moving Shot skills turn sideways like Dante.
Naturally, this affects the gangstas in Grand Theft Auto: San Andreas. You even see CJ using it with Guns Akimbo. (He even fires a pair of sawn-off shotguns this way if you level your skill with that weapon up all the way.) Note that all other weapons are held conventionally (well, as conventionally as possible, for the minigun). This is also the standard stance for Mafia, highway patrol, and SWAT teams – as an exception, standard police patrols hold their pistols with both handsnote a rather simple Game Mod allows all characters to do the same.
Falco holds his Blaster this way in Super Smash Bros. Melee. Granted, a laser gun probably wouldn't have the same issues facing it as a real gun.
The box art for Mega Man ZX Advent depicts Grey holding two energy pistols gangsta style.
Also, Omega in Mega Man Zero shoots his pistol buster like this, which is odd, considering that since they went to the trouble of making a new sprite for the pistol shooting, why not give him an Arm Cannon?
In the Wii video game Red Steel, the player can fire his gun gangsta style if he turns the controller sideways.
In LEGO Star Wars: The Original Trilogy, Lando would hold his blaster sideways.
R Amarls (Ranger + Human + Female) in Phantasy Star Online fire pistols like this. Ironically, this allows them to fire a bit faster than other classes, making them the best users of handguns in a case of Awesome yet Practical (though like the Falco example above, they are photon handguns, so...)
City of Villains, Troperiffic as ever, has the Thugs summoned by Masterminds (and the Masterminds themselves) use dual pistols like this. One of the reasons the players have been begging for years for a fully fleshed-out powerset to be given to the ranged combat classes.
And now those who have pre-ordered 'Going Rogue' have access to the Dual Pistols power sets for Blaster, Defenders and Corruptors that employs Gunfu with liberal amounts of sideways shooting.
In Vampire: The Masquerade – Bloodlines you don't actually get to use this mode of fire, but Romero the Ghoul provides some advice on gunfighting that includes "keep that glock-to-the-side crap in the movies."
In Silent Storm German soldier-class characters fire heavy machine guns sideways on full auto with one hand.
Similar to the above example, enemy Brutes in Uncharted 3 can do this with the PAK-80 LMG. The worst part about it is that they still hit you. Repeatedly.
In Blood 2 the alternate fire for the single pistol fires the gun this way and increases the rate of fire. It's apparently an emergency mode to quickly empty the pistol into a close-range attacker. Notice how Caleb points the barrel downwards as he shoots.
The special sniper rifle from Modern Warfare 3's "Eye of the Storm" mission can be fired in this manner if the player switches to using the red dot sight on it. Said sight is mounted 45 degrees on the left side of the barrel, though, so the gun is tilted in the opposite direction you'd expect.
While you can't actually see your weapon being held like this in House of the Dead: OVERKILL, the game recognizes when you hold the Wiimote sideways and will give you a $1337 post-chapter bonus for killing 50 mutants in this manner.
Averted in the 50 Cent game series. Mr. Jackson and his cohorts fire their armament in the standard manner, though foes will occasionally cant their guns the ninety degrees required of this trope.
In Saints Row 1, all gang members hold their handguns like this unless they're using two. In the sequels, everyone holds every gun upright at all times.
In the Rainbow Six: Vegas games, characters do this when using a ballistic shield, so it's not as awkward to fire.
This can be done in Jurassic Park: Trespasser, since the game lets you rotate the objects in your hand (including guns) in any manner you liked. It serves no practical purpose and absolutely kills your long range accuracy (assuming you don't line the sights back up), but it does look cool.
In Poke646 You can do this with the nailpistol, which lowers the accuracy and heightens the fire rate. But because the weapon in question looks like a big blue drill, it does not look cool here either.
In Team Fortress 2, the user-created randomizer mode randomly assigns you a class and weapons. If the Medic gets a gun, he holds it this way due to the way he usually holds his Medigun.
Jak and Daxter's Jak occasionally does this when firing the scatter gun.
In the Quake I total conversion Malice the protagonist fires his .44 automatic like this.
In Splinter Cell Conviction and Blacklist, Sam Fisher and other agents hold his gun heavily tilted to the left while holding it with both hands, although it's more a realistic depiction of Center Axis Relock (see 'Real Life' section below) than typical examples.
Syndicate (2012) had 45 degrees offset iron sights on the ACR assault rifle, with an attachment. This meant you could fire in automatic, then tillt the gun back to vertical and start firing in a more powerful scoped semi-auto mode.
Phantom of Inferno: Drei holds her pistols like this, owing to her love of dumb action movies. While the man who trained her actually notes that it's totally useless as a marksmanship technique, Drei later moves on to giving her opponent a chance to shoot her, twirling her guns and yelling out catch phrases in the middle of a gunfight, so she's clearly not at all concerned with anything but Rule of Cool gun-handling techniques. She's sixteen, which might explain it somewhat.
In Rose Guns Days, Leo wields his gun this way. As a former instructor in the army he probably knows it's completely useless, but since the character basically runs on Rule of Cool, that's not too surprising…
The Whiteboard has Doc customizing a marker so that a customer may shoot in this style.
Occasionally police officers using armoured shields will hold their pistols like this so they can see their sights through the window in the shield. That's about the only time you will see someone competent doing this in real life.
Members of the United States military are trained to hold their rifles sideways when wearing gas masks, as the design of the mask is too bulky for standard sighting. The M16 has a selectable rear sight with a larger peep hole designed for quick acquisition of targets at shorter ranges or in low-light conditions, however it also makes it easier to use when looking through a gas mask.
The famous Mauser C96 'Broomhandle' was only used as a primary service firearm by one nation: the Republic of China. Except they modified it with automatic fire and a much larger cartridge when they were invaded by Japan. This weapon could only be effectively used firing sideways (in Gangsta Style), or else the huge recoil would spray the gun straight up (when held sideways the recoil would shift accordingly, which is actually highly effective as it can sweep a room out), or the already-fired cases would fall back into and jam the gun.
The Darwin Awards gave an Honorable Mention to a man who attempted to fire a high-power pistol this way at a firing range, the recoil causing it to fly back and smack him in the mouth, knocking out several teeth.
December 10, 2009: fleeing from police through crowded Times Square, scam artist and sometime rapper Raymond "Ready" Martinez draws a Masterpiece Arms pistol (basically a modern clone of the Ingram MAC-11), holds it sideways in the best "gangsta" fashion and pulls the trigger. The weapon jams after two shots (with a spent casing falling back into the ejection port), both shots fail to hit anyone, and police return fire and "Ready's" criminal career comes to a swift conclusion. Had he held the gun correctly, the jam would have been averted and the loss of life could easily have been much worse.
It's said by many that this trope was adopted by modern gangsters from film stuntmen who turned their guns sideways to avoid ejecting hot shells onto each other. That said, ejecting straight upwards tends to drop spent casings directly down the shooter's collar; definitely a lateral move. Except the case in which the gangster is using is left hand in the case of a weapon designed for being held by right-handed people or using the right hand in the opposite cases.
The guy in the front seat during a drive-by would hold his weapon on its side so that the ejected casings wouldn't be propelled into the rear window - instead they would be ejected up onto or over the top of the car.
Another understandable reason is that when one has not been formally trained in shooting, the heaviness of the gun can make a sideways hold "feel" more natural.
Tilting a handgun about 20-30 degrees can help recoil management, and is often taught as a technique for shooting one-handed, with the off hand. However, a 90 degree tilt results in a weaker grip than normal.
The Nerf N-Strike Deploy CS-6 gun has its targeting light flipped to the left of the barrel, which may necessitate this. Sure it's got regular sights, but being sponge darts launched at safety speed, the drop in the trajectory makes a targeting light below the barrel more practical.
Going back a few generations in firearms design, this was the only practical way to ensure that a wheellock actually fired. Given the design of the action, turning the gun at least 45 degrees (NOT 90 degrees) was the best way to make sure that the powder was close enough to the sparks to actually go off. (Specifically it puts the sparks directly over the priming charge so that they fall into it rather than some of them going over the side and being wasted.)
There actually exists a shooting system in which the firer cants their pistol 45 degrees or more to the side. It is known as Center Axis Relock (CAR) and it is used by many law enforcement, security, and armed forces groups as a method of close quarters shooting. The technique is actually extremely effective for trained shooters and can be applied to rifle and shotgun shooting in close quarters as well. Watch a demonstration Here. This technique is SCARY effective at helping the shooter cope with recoil, as seen Here where a shooter fires a 12-gauge shotgun as though it were a pistol. Here's an explanation of the physiological flaws of Gangsta Style and the strengths of CAR.
Another consideration is that many techniques for disarming a guy with a handgun are meant to be used when the opponent is holding it vertically, and need to be adapted and practiced in order to deal with an opponent holding it in this manner. Though in some cases, being held up this way allows for easier disarming.
Something like this does get used by some military units, called an Ambi stance. It's used when breaching a room, if you catch a hostile in your peripheral vision, to bring the gun to bear as fast as possible, before following round into a proper shooting stance. It's not used for protracted periods of time.
This is similarly impractical with airsoft guns that use hop-up to make pellets fly further. Firing one in this manner can cause the pellet to curve in-flight.
A police officer in Missouri related that a gangsta took a shot at him with a Calico M-950. The M-950 has a 50-round magazine, but it also has idiot-proofing — it ejects spent casings downwards, using gravity alone. The gun jammed on the first shot and the policeman tackled his assailant.
Spoofed in the Birdman Weapon Systems◊ "Homeboy Nyte Sytes" for glock pistols, effectively adding secondary sights that can be used when firing the gun sideways.
Canadian firearms safety instructor Terry Pratt developed a system for people with cross dominant eyes to effectively fire a pistol. If, for example, your dominant eye is your left eye but your dominant hand is your right hand, you would tilt the pistol 45 degrees to the left as to allow your left eye to line up the iron sights.
In the US Army, people are allowed to choose their firing side, and about half of left-handed people fire right, while 10% of right-handed people fire left. If someone is having difficulty, a drill sergeant may check their eye dominance, and if they have cross dominance, suggest they switch hands. It is not hard to fire a US military M-16A2 with your non-dominant hand, unless there is something wrong with it (in which case, you probably won't be in the army).
Actors don't like anything that blocks their faces, leading to lots of laughably unsafe things, like military movies, where soldiers don't wear the chinstraps on their helmets, or don't wear helmets at all. The sideways gun may be a Hollywood invention, so you can see the actor's face when he holds the gun.