Sock It to Them

When a character uses a sock with a heavy object inside it as an improvised flail. The most commonly used items in fiction are coins (preferably rolled) and bars of soap. With coins, the most commonly used are nickels and quarters. Five dollars worth of nickels has the same mass as three baseballs, so it's easy to imagine the damage one of these weapons can do if swung fast enough.

Sub Trope of Improvised Weapon.

Anime and Manga

 * A sock full of coins is used as a murder weapon in Detective Conan.

Film

 * Death Wish has a scene where Paul Kersey attacks a mugger with a sock filled with quarters.
 * Previously, he had been practicing using the sock in his apartment and attacked a chair with.
 * The infamous "blanket party" scene from Full Metal Jacket, where everyone puts a bar of soap in a sock, and participates in a run-by pummeling of Vincent D'Onofrio.
 * The Grifters has a discussion on the pain and damage that can be inflicted with a sack filled with oranges.
 * Mallrats: "Phase one: First you take a run at La Fours with a sock full of quarters. I'd do it, but I pulled my back out humping your mom last night. Nootch. Okay, you clock him on his headpiece and knock his ass out cold. That's when phase two kicks in. I attack the structure Wolvie-Berzerk style, and knock out the fuckin' pin and bickety bam, the motherfucker is rubble. Hence, no game show."

Ultimately, the would-be assaulter slips, accidentally tosses the sock full of quarters in the air, and crashes, the sock of quarters landing neatly in the confused target's hands.
 * Heavenly Creatures ends with a murder committed with a brick in a nylon stocking.
 * Scum had an infamous scene where Carlin (Ray Winstone) assaults Richards (the lackey of Banks, the "daddy" of the Borstal) with two snooker balls in a sock.

Literature
"Coin: You're going to fight them with a sock full of sand?
 * The Dilbert special book Dogbert's Clues for the Clueless explained that, though tube socks and a paperweight make useless gifts by themselves, they can be combined into something useful for assaulting the gift-giver.
 * In Sourcery, Rincewind attempts to fight the Sourcerer with a half-brick in a sock. He later fills his other sock with sand in the Dungeon Dimensions.

Rincewind: No, I'm going to run away. The sock full of sand is for when they follow me."

Live Action TV

 * Thirty Rock: A drunk woman challenges Liz to a fight, and tells her she has two minutes to fill a sock up and meet her outside.
 * Arrested Development mentions a sock filled with nickels in a play being put on by the warden.
 * Played with in an episode of I Carly, where Sam lays into a writer with a sock full of butter.
 * There was an episode of Monk where a guy did this to himself: He tied the sock weapon to a ceiling fan so as to give himself contusions and frame another man.
 * The Janitor on Scrubs claims that his father used to do this. It's unlikely that he was telling the truth, of course.
 * In one episode of Seinfeld, Kramer and Newman reverse their peepholes "so they can tell if somebody is hiding in their apartments with a sock filled with pennies". Later in the episode, an acquaintance is attacked by their superintendent (under the belief that he was sleeping with his wife) a sock of pennies.

Web Comics

 * Used in an Imagine Spot in Johnny Wander, as the characters discuss what to do with $50 worth of small change.

Western Animation

 * Family Guy: After Meg gets out of prison, Connie D'Amico and her friends are teasing her in the school cafeteria. Meg ignores them and buys a bunch of soda cans from a vending machine. She loads them into a bag, and uses the bag on the group Batter Up style.
 * The Simpsons: When Homer and his buddies become a vigilante force because the police can't catch the Classy Cat Burglar stalking the neighborhood, Jimbo joins. He's told that his Weapon of Choice should be sack full of door knobs (a news anchor interviewing Homer later mentions that beatings with such a weapon have skyrocketted).
 * In the South Park episode "Lice Capades", Kenny is accused of having lice and gets beaten by the other kids with socks with a bar of soap in them.

Real Life

 * There's a rumor/urban legend that Bing Crosby beat his children with a sack filled with oranges, because that would cause serious pain but no visible bruises or internal injury. The Grifters claims the opposite effect (nasty looking bruises if done correctly; internal injury if not).