Weapon Stomp

The concept: Two people are fighting. Either with swords or guns, doesn't matter. One person loses their weapon in the fight and it goes skittering across the floor (usually toward the foreground). That person dives for it or crawls to get it, dramatically... but just as their hand reaches out to grab the handle/hilt—you see their opponent's foot come down upon the weapon (or on their reaching hand), ending the battle.

A sister trope of Gun Struggle, and a Gun Struggle often contains one of these.

A corollary trope would be where the character almost has a grasp of the weapon and is suddenly pulled back from it (or the weapon is kicked farther away). This usually results in another scramble for the weapon, often by both participants in the battle.

Examples of Weapon Stomp include:

Anime

In the Sailor Stars anime of Sailor Moon, Sailor Star Fighter falls holding the Sailor Star Yell while fighting Sailor Galaxia. When she attempts to raise it, Galaxia stomps on her hand, breaking the Sailor Star Yell with it.
Subverted in Berserk: Guts didn't lose his weapon when he fought Griffith the first time, but Griffith attempted to win the fight by jumping up and balancing on Guts' sword, trapping it against the ground.
Near the end of the last episode of Cowboy Bebop, Spike and Vicious are fighting. Each knocks the weapon out of the other's hand. As the weapons go skittering across the floor, Vicious steps on Spike's gun, but Spike grabs Vicious' katana. After a brief standoff, Spike tosses the katana back to Vicious as Vicious kicks the gun back to Spike.
Magical Girl Lyrical Nanoha StrikerS used this in a nasty way with one of the characters' Power Fist. We didn't see the actual battle, but considering how the stomped weapon was lying in a pool of blood and how the hand of said character was hidden during the entire scene, it's easy to guess how the character was disarmed for this trope to happen.
In Mai-Otome Zwei, Haruka stops on the gun of one of the busjackers after all of them are knocked down or out and their bomb is disabled before delivering a brief "The Reason You Suck" Speech about how they couldn't hope to win by taking hostages.

Film

This was done very nastily (but not that the guy didn't deserve it) in Shutter Island. The guy reaching for the gun had blown his cheek off in a suicide attempt and was lying on the floor bleeding out. He reached for his dropped gun to try again, only to have the protagonist step on it and drag it away.)
- To clarify, the man was a soon-to-be-captured Nazi who was trying to use suicide as an easy way out. Brutal, but as said, deserving.
There's at least one film version of Hamlet where this happens during the duel between Hamlet and Laertes. (I think it's the Kenneth Branagh version?)
The Film Version of The Lord of the Rings, Elendil's sword is shattered when Sauron steps on it. In a subversion of the trope, Isildur uses the shattered blade to cut Sauron's fingers (and thus separated him from the ring)
Pirates of the Caribbean II had Elizabeth going for the rifle, only for Jack to stomp on it. He then kicked it up so he could be the one to fire it.
- Norrington also did this with one of Davy Jones' mooks
Three Ten to Yuma had one of these; the stagecoach driver crawled for his shotgun but just as he got to it, Charlie Prince stepped on it.
Steve McQueen does this in Bullitt
In Anastasia, Rasputin's Soul Jar rolls away and she catches it under her foot, stomping on it with an "And This Is For" with each one.
James Bond does this to Alec Trevelyan's AK-47 during the train scene in GoldenEye.
A Cobra soldier does it to Scarlett's pistol in G.I. Joe: The Rise of Cobra.
Inverted in Mystery Men: The Shoveler stomps on his own weapon (a shovel) in order to flip it up into his grasp.
In Live Free or Die Hard, McClane's daughter shoves a gun toward him, as he is unarmed and hiding behind a car, but just as the gun gets to the car, the villain Gabriel stomps on it.

Literature

In the novel, Hannibal Rising (not sure if it's in the movie or not), Hannibal gets into a fight with Grutas, who is scrambling toward a gun; he steps on the gun and slashes Grutas.
In Starfighters of Adumar, Wes Janson disarms his opponent and breaks the blastsword by bringing the heel of his boot down on the right place. His opponent goes for his knife, but Wes kicks it out of his hand.

Live Action Television

In Firefly Atherton Wing does this to Mal, and breaks Mal's sword off at the hilt. Luckily for Mal, their duel then devolves a bit. Sword fighting? Not his specialty. But brawling he knows.
Mighty Morphin Power Rangers: During his first solo fight with Jason, evil!Tommy stomped on Jason's hand right after Jason had managed to retrieve his morpher. Fortunately for Jason the others were able to teleport him out.

Video Games

Awesomely subverted in Kingdom Hearts II. As Sora battles Roxas, Sora's Keyblade is knocked out of his hand as Roxas impales Sora's Keyblade with one of his own. However, Sora teleports his sword back to his hand and ends up being the one to deliver the finishing attack.
The corollary is shown in Bulletstorm, when Grayson is injured and crawls toward a PMC, which is kicked away by Sarrano.
Happens right at the start of Dragon Age 2, followed by a move dependent on Hawke's class (Mage!Hawke blasting the offending Hurlock's head off is the coolest, though).
Happens at the end of Call of Duty: Modern Warfare 2 as you're trying to get the Big Bad's gun to shoot him. He steps on the weapon right as you're about to grab it, then kicks you in the face.

Web Original

The web film Ryan Vs Dorkman 2 ends with Dorkman losing his sword hand to Ryan's saber. He tries to summon the saber to him with the Force, but Ryan's foot comes down on it and he proceeds to slice off the working end of the weapon, rendering it useless, before stabbing him in the shoulder to torture him (as he's been well into Dark Side mode for the majority of the fight). Dorkman proceeds to grab Ryan's saber and throw it, slicing Ryan in half and ending the fight.

Western Animation

In the cartoon version of Animal Farm (not sure if it's that way in the book or not), Mr. Jones loses his gun after Boxer the horse knocks him down. As he goes to reach for it, Boxer steps on it.
In an epsiode of G.I. Joe, Scarlett and Lady Jaye were leading a small band of captive women in an escape from one of Cobra's fiendish plots. They made short work of the guards that confronted them (it helped that Dr. Mindbender had ordered the women not be harmed). When one fallen Evil Minion attempts to reach for a firearm, Lady Jaye not only steps on his wrist, but catches it in her three-inch heeled shoe.
Batman has done this at least once in Batman: The Animated Series.
Subverted in Avatar: The Last Airbender in the fight between Piandao and Sokka; Sokka gets to stomp in Piandao's sword but he uses a lever-like movement and frees his sword.
In the Family Guy episode, "The Hand that Rocks the Wheelchair", Good Stewie and Evil Stewie (It Makes Sense in Context) fight over a raygun. Good Stewie crawls to grab it, and reaches it just as Evil Stewie stomps on it.