Do Not Drop Your Weapon

Shoot half a magazine into someone's body and he shrugs it off as if nothing happened (maybe writhing in agony for a few seconds if you get lucky), keeping a firm grip on his gun. Shoot him one more time and he dies, signified by dropping his gun. Yet, this only happens when he dies, as if the gun were keeping him alive.

This is a common trope in video games with enemies that use weapons, especially in gun-based FPS games. Of course, it also applies to the player character, where this is almost always the case. This is generally an Acceptable Break From Reality (especially in the case of the player, where dropping your weapon could be very irritating), yet some games take it to a truly ludicrous degree: Enemies have a variety of long-winded pain animations that appear to be leading to death (even falling over), yet the true way to tell that they are really dead is when their weapon finally leaves their hands. This applies even if the enemy is rendered unconscious in anyway other than Non-Lethal KO, they won't let go!

Some games do avert this by allowing you to disarm enemies (and even have it work both ways in rare cases), but it still remains ubiquitous enough to be a common trope; it's easier to list aversions.

Action Games

 * In Indiana Jones and The Emperor's Tomb, knocking an enemy down with punches or a powerful enough gunshot will knock their weapon out of their hands. They can also do the same to you, and you can even lose Indy's fedora. This means that the end every fight can potentially be a Crowning Moment of Awesome as you stand over the enemy's body and put your hat back on smoothly.

Action Adventure

 * Assassin's Creed II lets you disarm opponents in more than one way. An appropriately-timed counter while fighting empty-handed lets you steal the attacker's weapon (provided he's not too tough), while the special attack for the Two Handed Weapon superset is a smash attack that knocks the defender's weapon away. The latter can actually be done to the player, and yes, this WILL disarm you of whatever weapon you're carrying (though it isn't Lost Forever; you can simply pick it back up or, failing that, return to your home and get it out of the weapons room again).
 * Played straight and averted in Batman: Arkham Asylum. Most mooks you fight in combat will drop their weapons when they're knocked down, to be picked up by other enemies. Knife-bearing mooks don't, and in stealth sections, mooks will never drop their weapon. If a mook grabs a gun while you're in a fist fight, it is immensely satisfying to knock it out of his hands with an offhand Batarang.
 * Averted in The Legend of Zelda the Wind Waker. Attacking an enemy enough can sometimes cause them to drop their weapons before death, after which they will scramble for a new one or simply resort to fisticuffs.
 * You could also pick up their dropped weapons, for the first time in a Zelda game (I think ?).
 * Played straight with Phantom Ganon, however.
 * In Mirror's Edge all the Disarm moves are also knockout moves, and there's no functional or obvious difference between a knockout and a kill. In fact, killing an opponent using a method other than a gun still counts towards the Pacifist Run achievement.
 * The Pacifist Run's achievement wording only says not to shoot them. Anything else is fair game.

Fighting Games & Beat 'Em Ups

 * Just about every Fighting Game that features weapons will have this even worse—the weapon won't leave your grip even after death or knockout. Whether it's Yoshimitsu's sword, or Maxi's nunchaku, they hold on to the bitter end, and beyond.
 * Averted in the Super Smash Bros. series when it comes to items like beam swords and ray guns. If you hurt a player enough while they hold an item, they will drop it. Natrually, the AI will have the items glued to their hands no matter how hard you smack them.
 * In Street Fighter II, Vega loses his claw after 14 parries, forcing him to continue bare-fisted. Street Fighter Alpha 3 gave him the ability to fetch it back.
 * Mostly averted in the Ryu ga Gotoku games, but played straight as well. Most weapon-wielding enemies can be forced to drop their weapons when hit with certain attacks (such as throws), but a few will hold onto them no matter how hard you hit them. Applies to the protagonist as well, but in a more logical way—he'll drop large weapons like garbage cans and bicycles if he's hit hard enough while carrying them, but not small weapons like guns and knives.
 * Interestingly played with in the UFC games. Instead of a weapon though, whenever someone is defeated, they spit out their mouthpiece.
 * Undercover Cops featured enemy grunts who wielded broken bottles, knives, short handled battle axes, torches, and baseball bats. Upon killing them, they do not drop their weapons.
 * In the original Double Dragon, the player can disarm and wield any enemy's weapon with the exception of the final boss Willy, who never drops his machine gun no matter what. The sequels would add more enemies with exclusive weapons such as stick-wielding fighters and shuriken-throwing ninjas.
 * Averted in the Alien vs. Predator arcade game. All four player characters are armed with a default weapon that they can lose at any moment.

First Person Shooters

 * Used in the Battlefield series in various ways. Most commonly, weapons will disappear completely, replaced by a pack that corresponds to that player's chosen class. (Battlefield 2142 waits a few seconds before dropping kits to prevent ragdolls from straying too far away, resulting in players that can't be revived.) Items can't be mix-and-matched between kits.
 * The Bad Company 2 entry changed it up so that you have to pick up weapons the kit. Arguably, the kit was much easier to get since they would always be easily spotted and didn't fall around when it was dropped.
 * BioShock (series) 1 and 2 subvert this; the weapons can fall out of sight when they die, but you can find ammo for that weapon on their bodies. This trope is also averted in BioShock Infinite, where you can use (temporary plasmids?) nostrums to kick your enemy's ass with his own gun
 * Played straight and Averted in the Call of Duty series: Held in the original Call of Duty, with an interesting addition: a helmet coming off also signified death. Deliberately subverted in Call of Duty 2, where the same animations could occur despite the enemy not yet being completely dead. In the case of dropped weapons, the enemy in question will pull out a pistol for a last salvo, or crawl toward his fallen weapon. Call of Duty 4 and Call of Duty: World at War would have dying enemies pull a pistol or or ready a grenade. The latter is harder to tell since they will look dead until you hear a "tink" sound and the grenade indicator appears. Every multiplayer since Call of Duty 4 has the "Last Stand" perk which would allow "killed" players to draw a pistol and fight until they are hit again or bleed out. Oddly enough they don't drop their main gun when they enter "Last stand". And finally (for now) Modern Warfare 2 has the deathstreak "Final Stand" that allows you full access to your weapons and should you survive long enough you get up with full health.
 * Black Ops has the Second Chance perk. Initially it functions like Last Stand, and when upgraded allies can administer a shot of morphine and get you back on your feet, good as new. Ultimately played straight, as players drop whatever weapon they were using when they die, Second Chance or not. Where the light machine gun or SAM launcher they were holding a moment before pulling their pistol goes, however, is anyone's guess.
 * Crysis: Shooting a helmet causes it to pop off, and that is survivable unless really powerful weaponry was used, like a gauss rifle, which kills when it hits any part of a normal human. The victim still grips his weapon when unconscious, though, and needs to be killed to make him drop it.
 * Interestingly, the laser pointer found on the SMG will shut off if the enemy carrying it dies. IIRC the flashlight does the same thing.
 * "Oops, I'm almost dead. Better turn off my flashlight first. can't go wasting batteries, you know."
 * It's pretty common for tactical lights and laser sights to be configurable with pressure switches... Though if that's what's going on here, why the player can't make use of this feature is a bit of a mystery.
 * Averted in the Dark Forces series, at least Jedi Outcast and Jedi Academy: one of the easiest Force tricks you can do is yank your foes' weapons out of their hands with Force Pull. Some enemies, particularly fellow Force users, resist or block this and could even do the same to you with a strike.
 * Thrown lightsabers always return to the hand, but some bosses deflect it in such a way that it doesn't, and you have to make an extra effort to call it back to you.
 * There were a handful of other circumstances under which foes would drop their weapons and rather sensibly just run away.
 * Averted in Fallout 3, where guns can be shot out of enemy hands either manually or by targeting them with VATS. The usual response is to whip out a sidearm and keep fighting; if they don't have one in their inventory, they'll generally instead try to run and pick their weapon back up.
 * Arm-crippling seems to be useless other than dropping their weapon for some seconds. It doesn't even affect their accuracy.
 * Also averted in earlier Fallout titles, though weapons were only dropped after a Critical Failure, which is quite rare without a specific trait.
 * Averted and played straight in Fallout: New Vegas: depending on the physics involved when you kill an enemy, they may drop their weapon (particularly if Blown Across the Room), or they may still be clutching it when they die. The latter is pretty rare. However, though you can take advantage of the AI to make an enemy switch weapons, you can't make them drop them.
 * Averted in Far Cry 2, where enemies shot in the arm can drop their weapons, resulting in them pulling out a sidearm. Get them to drop that, and they run away.
 * Golden Eye 1997 and Project IGI take this a step further: You can kill enemies by shooting their guns!
 * As do the Halo games. The theater in Halo 3 allows you to go back and pinpoint the exact frame a player dies with this method.
 * Except for the Flood. When you fall down and drop your gun after a shot to the head, you DIED, dammit!
 * In Perfect Dark, you can non-lethally disarm enemies by Blasting It Out of Their Hands.
 * In Medal of Honor: Allied Assault, it is possible to knock down an enemy and make them drop their rifle. They will go crawling after it, trying to get up.
 * Aversion: In Perfect Dark, it's possible, albeit tricky, to shoot guns out of guards' hands. There are also certain weapons that disarm people (such the melee secondary attack). In multiplayer (and rarely in single-player) games it is also possible to be disarmed yourself.
 * On the other hand, in multiplayer mode, it is not possible to shoot someone's gun out of their hand without a disarming weapon. Although they do not take damage, shooting another character's gun will cause them to be knocked backwards as if you'd hit them.
 * Shooting the gun out of their hands, a staple of good guys in the more G-rated Western films and TV series, is featured in Red Dead Redemption. It's a good way to win pistol duels and is required for certain in-game marksmanship achievements, but normal enemies so disarmed will often quickly retrieve the weapon or continue fighting with another gun. Handgun-wielding foes who lose their gat may even produce a rifle from their Hyperspace Arsenal after running scared for a short time.
 * Averted in the multiplayer First-Person Shooter Red Orchestra: Ostfront 41-45, where guns can be shot out of your hand. This naturally leads to a frantic search for your weapon in the open.
 * Annoyingly, dropping a weapon (regardless of whether you were forced to or not) would also drop all your ammo for that weapon - meaning you not only have to find a gun, you have to fumble around for individual clips and magazines. This does make certain deaths comical as some players tend to horde ammo of all kind and it all explodes from his pockets when he is killed.
 * In Soldier of Fortune 1 and 2, enemies could be disarmed by Blasting It Out of Their Hands. In the first game, this effectively neutralized them as a threat, since they'd immediately cower and beg for mercy. In the second game, they're smart enough to whip out their sidearm if they have one, or run around looking for another weapon if they don't.
 * In Team Fortress 2, one of the biggest incentives to kill an enemy can be for their weapon, which restores half of your ammo reserves, and your cloak as a Spy.
 * The Spy's alternate cloak watch, the Dead Ringer, will spawn an extra weapon to make the illusion seem real, though it can't be retrieved to restore ammo (which is a telltale sign of the Dead Ringer any competent player should watch for).
 * Wonderfully averted in TimeShift: Shooting an enemy in the arm will usually make him drop his weapon. Hilariously averted when you freeze time, steal a weapon right out of an enemy soldier's hands and then shoot his allies with it before normal time resumes.
 * In Time Splitters, the enemies everywhere flop wildly when they get hit. Seeing as they take multiple clips before they die on the harder levels, this soon becomes very annoying, as they practically dance across levels. True death only follows when their weapon shoots out of the hands onto the ground 10 feet in front of them.
 * It's possible to punch or kick weapons out of player's hands in the Half Life mod, The Specialists. It's also then possible to grab the weapon as it's flying through the air and shoot the original owner with it. However, it's not possible to shoot weapons out of player's hands.

Hack and Slashers

 * In Dark Messiah, often the easiest way to tell if an enemy is dead is to check if he is still holding his weapon, since all regular enemies drop their weapon when they die, and only when they die. Enemies often fall down and stop moving when they are near to death, looking very much like dead, but are actually alive and able to rise and attack the player again. Therefore it would be dangerous for the player to turn back on them. Usually in this kind of situation the only way to make sure the enemy is really dead is to keep attacking the recumbent foe until you see him let go of his weapon. Though subverted in that by spending experience points in melée combat one can disarm an oppenent under certain circumstances at which point the enemy will attempt to recover the weapon as soon as possible or attack you unarmed. Also, archers will switch to their sword if you trap them in a corner and get too close for comfort, dropping the bow on the ground.

RPGs

 * Elder Scrolls: Oblivion averts this. You can disarm enemies, and your opponents can disarm you, too.
 * Averted a second time in that dead enemies may keep a firm grip on their weapon even after being killed. Skeletons can even be blasted apart and their severed hand will still be tightly gripping their weapon! You can still take it from them by looting their corpse, however.
 * Averted in Gothic - simply knocking out an NPC is enough to make him drop his wielded weapon. Unfortunately, this also applies to you. Savvy players will quickly sheathe their swords just as they're about to be knocked out, as NPCs will pick up and keep any weapon that falls from your hands, but won't bother going through your inventory for it; and will already have stashed their gold somewhere else, as guards won't pick up gold from the floor, but will eagerly pick your pockets for it when you're down.
 * Averted hard in Skyrim. The Disarm perk in the Block skill tree allows you to bash weapons out of an enemy's hands. The "Disarm" Dragon Shout does the same thing—which is bad news for you when you face higher-level Draugr that can use that Shout. After being killed, enemies usually lose their grip on their weapons. You can still loot the corpses to get the weapons, but you can also just pick up the weapon itself.

Run And Gun

 * In most Sega gun games in which your opponents are armed, any shot that hits will kill, but you get bonus points (and sometimes powerups) for disarming "skill shots." This becomes very important in Rambo, where trick shots power up your Rage Meter.

Side-Scrolling Shooters

 * Halo Zero also does this, due to the limitations.

Simulation Games

 * Dwarf Fortress let both your dwarfs and enemy goblins become disarmed due to injury. It's also possible for a weapon to get stuck inside a target's body, or taken away via wrestling. However, in Adventure Mode, NPCs do not drop their weapon when they fall unconscious, only when their ability to grasp specifically has been impaired, because they won't pick up any item and thus would become permanently disarmed.

Survival Horror

 * Certain psychos in Dead Rising 2 can make you drop your weapons; chiefly, the redneck security guard who can blast them out of your hands.

Third Person Shooters

 * Averted in Gun, which actually gave you bonus points for disarming your enemies (as well as counting as a kill). However, this can be tricky unless one uses the game's Bullet Time power.
 * In the default Max Payne, the enemies only drop their guns when they die. However, some mods, e.g. the Kung Fu Mod, would make them drop them when their health drops below certain threshold, presumably as if their hands were too weak to hold them. However, they then usually go on to attack Max on close-range... with spinning and flying kicks, no less, which makes you wonder where did THAT strength come from.
 * Averted in Metal Gear Solid 2 and onward: Shooting an enemy's hand will cause him to drop his weapon. As long as he's not a boss. Or you.
 * In at least MGS4, when you tranquilized an enemy with a rifle, they'd drop it when they passed out. If you then took it from him, he'd pull out a pistol when he woke up. If you repeated the process, he'd just get up and continue to run his designated patrol completely unarmed. I never found out if they'd try to punch you if they caught you like that.
 * For anyone curious, they use a knife and try to stab you instead.
 * Actually, the pistols respawn eventually.
 * Averted in Oni where not only can you use a disarm move to take someone's gun, but throwing or knocking your opponent down in melee will also cause any equipped weapon to be dropped.

Turn-Based Strategy

 * In Fire Emblem, certain enemies will drop their weapons (or other cool prizes) when defeated. However, if the object is not equipped, you can have a thief walk up to the enemy unit and use the "Steal" option.
 * Averted in Jagged Alliance 2, where all sorts of things could cause a character to drop his weapon, particularly the use of stun grenades and other explosives. This includes both friends and foes. However, to keep the player from getting too many powerful weapons in the early stages of the game, some enemy weapons disappear completely once the enemy carrying them dies, for no other reason. This leads some players to try and "steal" weapons from enemies before killing them, which verges on suicidal unless you're really really good at it.
 * The reasoning behind this is shown in the 1.13 fan-patch, which allows you to force enemies to drop their weapons: after clearing a heavily defended sector at the beginning of the game, you will find yourself flooded with new weapons, only a couple of which you might even want.
 * The X-COM games play it mostly straight. Enemies only drop their inventories when dead or unconscious. That is, unless you exploit a minor bug in the first game or they are caused to panic (psi attacks, killing their own men, and killing them can do this). Also, they cannot pick up said weapons, apparently due to failure to update game data when this feature was overhauled (it's easily fixed in Game Mods, even for the original game). Then again, if an alien dropped the gun but also has a grenade in equipment, that's what you'll get on the next turn.

Wide Open Sandboxes

 * Averted in Cortex Command, where disarming is so ridiculously easy that sometimes even the recoil of your weapon can disarm you. And weapons aren't indestructible either. Dying by stepping on a grenade to hard sucks...
 * Averted in Grand Theft Auto IV, in which NPCs drop their weapons under a variety of circumstances besides dying. In melee combat you can steal a knife right out of your opponent's hands if you dodge at the right moment, while you can knock a gun out of out of their hand with a whack from the baseball bat. You can also shoot a person's weapon out of their hand, in which case they'll retrieve a backup (if they have one) or otherwise resort to fisticuffs. In an extreme example of this, this troper once shot a NOOSE operator's M4 out of his hands, so he retrieved a shotgun. I shot that out of his hands, and he retrieved a Glock.